In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Comprehensive Guidance of The Messenger – By Imaam Ibnul Qayyim [rahimahullaah]
Imaam Ibnul Qayyim [rahimahullaah] said: Muhammad’s [sallal-laahu-alayhi-wasallam] Ummah is not in need of anyone after him; rather the only need they have is someone to convey what he came with. Muhammad’s [sallal-laahu-alayhi-wasallam] message is comprehensive, universal and preserved. This universality, comprehensiveness and preservation is not limited to [any time and place], rather it is comprehensive for those to whom Muhammad [sallal-laahu-alayhi-wasallam] was sent [i.e. the whole world] and likewise with regards to everything that is needed in the fundamental and subsidiary issues of the religion.
Muhammad’s [sallal-laahu-alayhi-wasallam] message is sufficient, all embracing and universal- nothing else is needed besides it. It has not isolated any affair of truth needed by his Ummah in their sciences and deeds. The Messenger of Allaah [sallal-laahu-alayhi-wasallam] did not leave this world until he acquainted his Ummah with everything. He even taught them the etiquettes of using the toilet; the etiquettes of sexual relations; the etiquettes of sleep and after waking up; the etiquettes of eating, drinking and travel.
He acquainted them with the etiquettes of speech and silence; the etiquettes of keeping company with the people and seclusion. He acquainted them with the affairs of illness, good health, poverty and wealth. He acquainted them with all the affairs of life and death. He described Allaah’s throne, the angels, the jinn, the hell fire and the day of judgement in such a manner as if one has seen them with the naked eye. He [sallal-laahu-alayhi-wasallam] informed them about their Lord and His Perfect Names and Attributes, and that Allaah alone is their true object of worship.
He acquainted them with the Prophets of old and their nations – the events that took place between them and their nations – in such a manner as if one was present at that time. He acquainted them with all the means to good and the paths of evil- in general and in detail- which no other prophet informed his nation. He acquainted them with death and what will take place in the grave – either bliss or punishment. He acquainted them with the evidences and proofs of Tawheed [i.e. the oneness of Allaah in His Lordship, Names and Attributes, and that Allaah alone has the right to be worshipped].
He acquainted them with Prophet hood and the affairs of the Afterlife, and he refuted all the sects of disbelief and misguidance. He acquainted them with war strategies- how to confront the enemy, the way to achieve victory and conquests. If only they knew and understood these affairs in the correct manner [i.e. the manner it should be understood], they would not be overcome by their enemy. He acquainted them with the plots of Iblees and the ways through which he approaches them, and the ways to repel those plots and plans. He acquainted them with the soul- its characteristics and faults- in such a manner that they are not in need of anyone else to tell them about it. He taught them how to live their daily lives and had they acknowledged and acted upon this; their worldly affairs would be firmly established. He brought them all the means of success in this life and the next, and they do not need anyone besides him. So how can it be said that the path of Muhammad [sallal-laahu-alayhi-wasallam] is in need of something else outside of it. The reason for such a claim is due to the weak and little understanding of a person. Allaah [The Most High] said:
أَوَلَمْ يَكْفِهِمْ أَنَّا أَنزَلْنَا عَلَيْكَ الْكِتَابَ يُتْلَىٰ عَلَيْهِمْ ۚ إِنَّ فِي ذَٰلِكَ لَرَحْمَةً وَذِكْرَىٰ لِقَوْمٍ يُؤْمِنُونَ
Is it not sufficient for them that We have sent down to you the Book (the Qur’an) which is recited to them? Verily, herein is mercy and a reminder (or an admonition) for a people who believe. [29:51]
Allaah [The Most High] said:
وَنَزَّلْنَا عَلَيْكَ الْكِتَابَ تِبْيَانًا لِّكُلِّ شَيْءٍ وَهُدًى وَرَحْمَةً وَبُشْرَىٰ لِلْمُسْلِمِينَ
And We have sent down to you the Book (the Qur’an) as an exposition of everything, a guidance, a mercy, and glad tidings for those who have submitted themselves (to Allah as Muslims). [16:89]
Allaah [The Most High] said:
يَا أَيُّهَا النَّاسُ قَدْ جَاءَتْكُم مَّوْعِظَةٌ مِّن رَّبِّكُمْ وَشِفَاءٌ لِّمَا فِي الصُّدُورِ وَهُدًى وَرَحْمَةٌ لِّلْمُؤْمِنِينَ
O mankind! There has come to you a good advice from your Lord [i.e. the Qur’an, ordering all that is good and forbidding all that is evil], and a healing for that [disease of ignorance, doubt, hypocrisy and differences, etc.] in your breasts, – a guidance and a mercy [explaining lawful and unlawful things, etc.] for the believers. [10:57] [Ref 1]
One of The Noblest Aspects of Knowledge Is to Pay Attention to The Characteristics of The Messenger [sallal laahu alayhi wasallam] – By Shaikh Abdur Razzaaq Al-Badr [hafidhahullaah]
Shaikh Abdur Razzaaq Al-Badr [hafidhahullaah] said: Indeed, one of the greatest bestowals on a believing slave of Allaah – which leads to guidance and righteous deeds -is that Allaah [The Mighty and Majestic] facilitates for him the path to seeking knowledge, grants him an ardent zeal and eagerness for knowledge. Seeking knowledge is something one never feels that he has acquired enough, rather whenever a path to knowledge is made available, he pursues it.
Allaah protects the student of knowledge, guides and aids him, therefore it is obligated on a student of knowledge to exalt the affair of turning to Allaah [in submission, obedience etc] and that what he learns should be a proof for him and not against him; and that Allaah increases him in knowledge, facilitates him with the path to good and guidance. “Whoever follows a path in search of knowledge Allaah will make easy for a him a path to paradise”.
One of the noblest aspects of knowledge – an affair that occupies a mighty station- is to pay close attention to the characteristics of the Prophet, his specific qualities and deeds by way of which Allaah distinguished him from everyone amongst mankind, his manners, etiquettes and biography. That is because he is the greatest Imaam [leader] and the perfect example. Indeed, Allaah [The Mighty and Majestic] commanded us to follow his example, made him an Imaam [leader] and example for us. Allaah [The Mighty and Majestic] said:
لَّقَدۡ كَانَ لَكُمۡ فِى رَسُولِ ٱللَّهِ أُسۡوَةٌ حَسَنَةٌ۬ لِّمَن كَانَ يَرۡجُواْ ٱللَّهَ وَٱلۡيَوۡمَ ٱلۡأَخِرَ وَذَكَرَ ٱللَّهَ كَثِيرً۬ا
Indeed in the Messenger of Allah (Muhammad) you have a good example to follow for him who hopes in (the Meeting with) Allah and the Last Day and remembers Allah much. [Surah Al-Ahzaab. Aayah 21]
This noble Aayah – as the people of knowledge have stated – is a basis to established the fact that the Prophet [sallal laahu alayhi wasallam] is to be emulated; [but] emulating him cannot be actualized except by way of acquainting oneself with his characteristics, his qualities in general, his specific qualities and deeds by way of which Allaah distinguished him from everyone amongst humankind, his manners and etiquettes. The one who is unacquainted with the Prophet’s [sallal laahu alayhi wasallam] characteristics and manners will not be able to emulate him, and that is why the scholars [of Islaam] have written beneficial books regarding his characteristics and qualities.
The manners and qualities of the Prophet [sallal laahu alayhi wasallam] are a means of inviting [mankind] to this mighty religion [of Islaam]. Indeed, many people- during his era and thereafter – have been guided through their acquaintance with his manners and qualities. One used to come to him whilst harbouring the severest hatred towards him, but after meeting him and [observing] his great [unmatched noble] etiquettes, noble manners, lofty dealings and benevolence, the person would depart whilst loving him more than everyone else on the face of the earth. Therefore, his characteristics are a means to calling to this religion- a weapon for the one inviting the people in the path of Allaah.
Speaking about his qualities, emulating him and calling others to emulate him strengthens the religion of Islaam, because he was the one whom Allaah appointed to convey and explain the religion to humankind. Allaah chose him and he is the best of all the slaves of Allaah- the greatest in his servitude to Allaah. Calling the people to emulate his qualities is a means to calling people to believe in the religion ordained by Allaah and a means to strengthening the belief of the one who has already believed in his Messenger-ship. This is why turning away from his Seerah has been the cause of people’s inclination towards the path of losers amongst men and women [i.e. those upon a path other than the path of Allaah]. As for the biographies of the Imaams of Guidance- the greatest of them being the Messenger, they are a means of rectifying the person and a means to safety from corruption and evil. On the other hand, the biography of the losers is a path that will lead to evil, ruin and corruption. Allaah [The Mighty and Majestic] said:
قَدۡ كَانَتۡ ءَايَـٰتِى تُتۡلَىٰ عَلَيۡكُمۡ فَكُنتُمۡ عَلَىٰٓ أَعۡقَـٰبِكُمۡ تَنكِصُونَ
مُسۡتَكۡبِرِينَ بِهِۦ سَـٰمِرً۬ا تَهۡجُرُونَ
أَفَلَمْ يَدَّبَّرُوا الْقَوْلَ أَمْ جَاءَهُم مَّا لَمْ يَأْتِ آبَاءَهُمُ الْأَوَّلِينَ
أَمْ لَمْ يَعْرِفُوا رَسُولَهُمْ فَهُمْ لَهُ مُنكِرُونَ
Indeed My Verses used to be recited to you, but you used to turn back on your heels [denying them, and with hatred to listen to them]. In pride [they Quraish pagans and polytheists of Makkah used to feel proud that they are the dwellers of Makkah sanctuary Haram], talking evil about it [the Qur’an] by night. Have they not pondered over the Word [of Allaah, i.e. what is sent down to the Prophet], or has there come to them what had not come to their fathers of old? Or is it that they did not recognize their Messenger [Muhammad] so they deny him? [i.e. this is a rebuke against them because all of them – young and old – knew his lineage, truthfulness and trustworthiness, yet they turned away from his message]. [Surah Al-Muminoon. Aayaat 66-69]
This shows that contemplating on the Qur’aan and acquainting oneself with the Messenger’s guidance and biography is a path leading to safety, and a safeguard against turning back on one’s heels [i.e. a safeguard against turning away from the guidance he was sent with]. On the other hand, abandoning the Seerah of the Prophet and inclining towards the Seerah of the losers [i.e. those men and women upon other than the guidance of the Messenger] will lead to ruin. The people became corrupted – in this era – after being put to trial through movies and films; but had they turned to the biographies of the Prophets and the noble companions of the Prophet Muhammad, they would have found guidance and a path leading to steadfastness. 
Reading The Biography of The Messenger Increases The Believer In Certainty – By Shaikh Saaleh Aala Ash-Shaikh [hafidhahullaah]
Shaikh Saaleh Aala Ash-Shaikh [hafidhahullaah] said:
Studying the prophet’s biography (sallallāhu alaihi wa salam) and reading it, makes the certainty of the believer to become stronger, makes his steadfastness and perseverance upon the religion of Allah stronger, makes the believer’s heart to be honourable due to Islam, ennobled by [his adherence to sound] Islamic monotheism, ennobled due to what his heart contains of knowledge and awareness of Allah, ennobled due to his belief in Muhammad (sallallāhu alaihi wa salam) and ennobled by that which Allāh sent down upon his Messengers. Allaah said: [وَلِلَّهِ الْعِزَّةُ وَلِرَسُولِهِ وَلِلْمُؤْمِنِينَ – But honour, power and glory belong to Allah, His Messenger (Muhammad sallallāhu alaihi wa salam), and to the believers]. [Al-Munāfiqūn 8] These are from the many benefits that every believer benefit from by studying the biography of The Chosen One (المصطفى) (sallallāhu alaihi wa salam). 
The Sound Religion Is What Will Rectify The Souls And Not The Modern Sciences- By Imaam As-Sadi [rahimahullaah]
Imaam Sadi [rahmahullaah] said:
Indeed, it is impossible to rectify the souls and acquire virtue solely through the worldly sciences. Experience and clearly witnessed circumstances are the greatest proofs regarding this affair, because despite its advancement and vastness it has been unable to nurture and rectify the souls [i.e. upon excellent traits, manners, dealings, characteristics, sound creed etc] which are the determinants of [sound] rectification and success. What the Religion of Islaam propagates is that which is entrusted with this rectification; it is what will guide the thoughts towards the truthful and authentic sources of knowledge, guide the actions of the people towards good and prevent them from evil. Islam is The Rectifier of the Creeds and Manners- the thing that cultivates the thoughts [upon righteousness], urges towards virtuousness and prevents from depravity.
The essence of that which the religion calls to – regarding belief in the Unseen, which includes belief in Allaah and that which He possesses of Names, Attributes and Actions of perfection; belief in Angels, belief in recompense for one’s good and bad deeds in this life and the next, which cannot be known except through the Messengers, is what acquaints a person with the fact that rectification – in reality – is not possible through other than sound belief and the religion of Islaam.
Therefore, even if the worldly sciences rectify [some] affairs based upon that which [some] people know in detail, it will still not be equal [in perfection, excellence etc] to the knowledge of the Messengers [in the least]. It will neither reach that which is reached through the knowledge of the Messengers nor can it influence the souls in the manner in which the knowledge of the Messengers has done; for indeed the souls do not voluntarily submit except through belief in Allaah, belief in His Angels, belief in His Books, belief in His Messengers and belief in the hereafter. And without this, voluntary submission is impossible, as is well known regarding human nature. [Ref 4]
Progress In The Worldly Affairs Is Sought After, But We Must Return to Our Deen- By Saudi King Abdul Azeez [rahimahullaah]
Saudi King Abdul Azeez [rahimahullaah] said: Indeed, the progress and advancement of the Muslims is among those affairs we [pursue]–we call to it by the will of Allaah. [However] there cannot be advancement for the Muslims without a return to their religion, adherence to their sound creed and holding onto the Rope of Allaah [i.e. the Qur’aan and the Sunnah]. The path towards this is clear and facilitated for the one who wants to follow it, and that is to single out Allaah in worship – to be free from shirk and bidah- and act on that which the religion has commanded us, for indeed there is no benefit in speech if not [accompanied] by action. [Ref 5]
The Evil Consequences That Will Accompany Worldly Knowledge When Devoid of Sound Religion- By Imaam As-Sadi [rahimahullaah]
Imaam As-Sadi [rahimahullaah] said: Industrialization And Modern Inventions: Everyone has participated in it – the righteous, the wicked, the believer and the disbeliever. As for religion and [virtuous] manners, then indeed -in this era-, it has greatly declined. So, when this industrial advancement is devoid of Deen and Eemaan, it became a great harm from two angles:
Firstly: It beguiled many people, who – due of their ignorance – think that worldly advancement is proof to show that its people are more worthy of achieving every good than others. They are clearly misguided, for indeed a person might be from the most skillful in affairs related to the material world, whilst he is one of the most ignorant people in affairs related to the deen, virtuous manners and the [other] beneficial affairs in this life and the next.
Secondly: When these inventions are devoid of Deen, its mercy and wisdom, it becomes a great disaster for humankind due to the wars that resulted from them, killing, destruction and other affairs related to it. Its regulators [or overseers] and scholars are unable to laydown – for humankind -a stable, just and good life, rather they have not ceased moving from one misrable state to another. This is inevitable and the continuous state of affairs shows that [to be the case]. Therefore all good is found in the sound religion and all evil is found in rejecting and willfully denying [Allaah, His Messengers, His Laws, Guidance, Commands, Prohibitions etc] [Ref 6]
The Correct Manner In Which to Approach The Contemporary Sciences – By Imaam Abdul Azeez Bin Baaz [rahimahullaah], Imaam Muhammad Bin Saaleh Al-Uthaymeen [rahimahullaah] and Shaikh Saaleh Aala Ash-Shaikh [hafidhahullaah]
Shaikh Saaleh Aala Ash-Shaikh [hafidhahullaah] said:
The Messenger [sallal laahu alayhi wasallam] said: Verily, the creation of each of you is brought together in his mother’s womb for forty days as a drop [of water, semen], then he is a clot for a similar period, then a morsel for a similar period…. [An-Nawawi’s Forty Hadeeth. Hadeeth 4]
It is well known that during that era, the Sahaabah did not know these stages [of development of the human being in the womb] through experimental knowledge, vision [i.e. by way of the naked eye] or other than that; rather it was simply [a statememt of the Prophet] which they [believed and affirmed]. They were scholars by way of the revelation sent down to the Prophet [sallal laahu alayhi wasallam] and not by way of experimentation [examination]. [Ref 7]
Imaam Muhammad Bin Saaleh Al-Uthaymeen [rahimahullaah] said:
We do not say: “We do not give consideration to anything stated by the people in the subject matter regarding medicine, astronomy and the celestial bodies”; however, we do not accept everything they say. If what they say opposes the Book and the [authentic] Sunnah, then indeed we do not accept their statements; [rather] we take [i.e. believe and affirm without any doubt] that which is conveyed in the Book and the [authentic] Sunnah, and we say, ‘An era will come in which the people will bear witness to the falsity of those statements of theirs – at present – that are in opposition to the Book and [authentic] Sunnah and [bear witness] to the soundness of that which has been conveyed in the Book and the [authentic] Sunnah. [Ref 8]
Imaam Abdul Azeez Bin Baaz [rahimahullaah] said:
Indeed, that which is stated by the astronomers about the celestial bodies, their sizes and the distance between them, and that which is said about the earth [i.e. by the geologists etc] is categorized into three affairs: [a] That which is backed by the sound knowledge-based proofs [i.e. the Sharee’ah], therefore it is accepted. [b] That which the knowledge-based proofs [i.e. the sharee’ah] declares to be false, therefore it is rejected. [c] That which there is no proof to either accept or reject it, therefore it is unproven until a person from the people of knowledge [i.e. upright scholars of Ahlus Sunnah] examines it [i.e. examines what it indicates based on the Book and Sunnah] to show whether it should be accepted or rejected. As for accepting it without [sound] investigation and observation, but merely accepting it by blindly following them [i.e. the astronomers, geologists etc], then this is impermissible because of the numerous mistakes that occur as a result of that, and speaking -without knowledge – about Allaah and that which He has created [i.e. the entire universe and all that is within it]. [Ref 9]
[Ref 1: An Excerpt from I’laam Al-Muwaqqi’een 4/375-377- slightly paraphrased]
[Ref 2: Source: An Excerpt from: [شرح المختصر في صفات النبي ﷺ وأخلاقه] Lesson 1. slightly paraphrased]
[Ref 3: Silsilatu al-Muhādarāt al-‘ilmiyyah Vol.4 Pgs. 506-507]
[Ref 4: Al-Adillah Al-Qawaati Wal-Baraaheen Fee Ibtaalil Usoolil Mulhideen 49-50]
[Ref 5: Haqeeqah Manhaj Al-Mamlakah Al-Arabiyyah As-Su’oodiyyah page 33]
[Ref 6: Al-Adilladul Qawaati 45-46]
[Ref 7: Sharh Al-Arba’een. Hadeeth 4]
[Ref 8: An excerpt from the ‘Explanation of Bulooghul Maraam’ Vol 1. page 130]
[Ref 9: An Excerpts from ‘Al-Adillah An-Naqliyyah Wal-Hissiyyah Alaa Imkaanis Su’ood Ilal Kawaakib Wa Alaa Jarayaan Ash-Shams Wal-Qamar Wa Sukoon Al-Ard’ page 74. slightly paraphrased]