In The Name of Allah, The Most Merciful, The Bestower of Mercy.
Imam As-Sadi [may Allah have mercy upon him] said:
You should be aware that the Islamic religion’s outstanding characteristics can be found in all of its subject matters and proofs – in its fundamental principles and subsidiary issues, in what the sciences and Shariah rulings demonstrate, as well as what it says about physical sciences and sound unity (social harmony, cooperation based on piety and righteousness to fulfil both religious and beneficial worldly affairs). The goal is not to include these matters in this discourse and explore them, as that would require a great deal of elaboration; rather, the goal is to cite useful examples that can be used as evidence for other matters, and thus open the door for those who want to enter into this topic. These are examples that can be found across the fundamental Islamic principles, subsidiary issues, mutual dealings, and those customary practices (of the people approved by Islam).
So, while seeking Allah’s assistance and hoping that He will guide and teach us, open for us the treasures of His kindness and generosity by which our circumstances will be rectified and statements and deeds will become upright, we say that Islam is based on the pillars of faith mentioned in Allah’s statement:
قولوا آمنا بالله وما أنزل إلينا وما أنزل إلى إبراهيم وإسماعيل وإسحاق ويعقوب والأسباط وما أوتي موسى وعيسى وما أوتي النبيون من ربهم لا نفرق بين أحد منهم ونحن له مسلمون
Say (O Muslims), “We believe in Allah and that which has been sent down to us and that which has been sent down to Ibrahim (Abraham), Isma’il (Ishmael), Ishaque (Isaac), Ya’qub (Jacob), and to Al-Asbat [the twelve sons of Ya’qub (Jacob)], and that which has been given to Musa (Moses) and ‘Iesa (Jesus), and that which has been given to the Prophets from their Lord. We make no distinction between any of them, and to Him, we have submitted (in Islam).” [Surah Al-Baqarah. Aayah 136]
These great principles, which Allah commanded His servants to observe, are universally acknowledged by all the Prophets and Messengers. They embody the loftiest aspects of knowledge and creed, such as belief in all that Allah has revealed about Himself through His Messengers, who exerted themselves in seeking Allah’s Pleasure.
The religion’s foundation is sound belief in Allah, and its fruitful outcomes are based on striving to pursue everything that is beloved to Allah -everything pleasing to Allah and sincere devotion to Him. So, can it ever be imagined that there is a religion better, loftier, and more virtuous than such a religion?! It is a religion that enjoins belief in everything that the prophets were given, belief in their messages, acknowledging the truth that they brought from their Lord, and not distinguishing between them by believing in some and disbelieving in others, (footnote a), and believing that they are all Allah’s Messengers- truthful, trustworthy, and sincere.
Given that Islam commands all truth, accepts all matters that are established on truth, and establishes religious facts based on Allah’s revelation to His Messengers, it is impossible for any (legitimate or sound) opposition or criticism to be directed at it. It agrees with the useful rational facts that are confirmed by (sound) natural disposition- neither rejects truth nor testifies to a lie nor can deception be promoted about it (without such lie being exposed for what it is) because it is dominant over all other religions. It enjoins good deeds, noble morals, (perfect) welfare for the people, justice, grace, mercy, and goodwill while condemning injustice, oppression, and bad manners. There is no perfect characteristic that the Prophets and Messengers affirmed, save that it has acknowledged and affirmed it. There is no religious or worldly welfare that the other divine laws of the Messengers called to, except that it encourages it, and there is no corruption except that it has banned and ordered that it be avoided. The purpose of this clarification is to make clear that this religion’s beliefs are those by which good morals and acts are well-established, as well as those by which hearts are purified and souls are rectified. (1)
Footnote a: Allah [The Exalted] said:
إِنَّ ٱلَّذِينَ يَكۡفُرُونَ بِٱللَّهِ وَرُسُلِهِۦ وَيُرِيدُونَ أَن يُفَرِّقُواْ بَيۡنَ ٱللَّهِ وَرُسُلِهِۦ وَيَقُولُونَ نُؤۡمِنُ بِبَعۡضٍ۬ وَنَڪۡفُرُ بِبَعۡضٍ۬ وَيُرِيدُونَ أَن يَتَّخِذُواْ بَيۡنَ ذَٲلِكَ سَبِيلاً
أُوْلَـٰٓٮِٕكَ هُمُ ٱلۡكَـٰفِرُونَ حَقًّ۬اۚ وَأَعۡتَدۡنَا لِلۡكَـٰفِرِينَ عَذَابً۬ا مُّهِينً۬ا
وَٱلَّذِينَ ءَامَنُواْ بِٱللَّهِ وَرُسُلِهِۦ وَلَمۡ يُفَرِّقُواْ بَيۡنَ أَحَدٍ۬ مِّنۡہُمۡ أُوْلَـٰٓٮِٕكَ سَوۡفَ يُؤۡتِيهِمۡ أُجُورَهُمۡۗ وَكَانَ ٱللَّهُ غَفُورً۬ا رَّحِيمً۬ا
Verily, those who disbelieve in Allah and His Messengers and wish to make a distinction between Allah and His Messengers (by believing in Allah and disbelieving in His Messengers) saying, “We believe in some but reject others,” and wish to adopt a way in between. They are in truth disbelievers. And We have prepared for the disbelievers a humiliating torment. And those who believe in Allah and His Messengers and make no distinction between any of them (Messengers), We shall give them their rewards, and Allah is Ever Oft-Forgiving, Most Merciful. [Surah An-Nisaa. Ayaat 150-152]
Read: All The Prophets Were Muslims and The Qur’aan Abrogates all Previous Laws of The Prophets: https://salaficentre.com/2020/10/18/one-must-call-himself-a-muslim-if-he-truly-follows-the-path-of-the-prophets-and-messengers/
Read: Are There Three Monotheistic Religions In The World at Present? https://salaficentre.com/wp-content/uploads/2021/02/Are_There_Three_Monotheistic_Religions_In-The_World_At_Present_Section1.pdf
[Ref 1: Ad-Durra Al-Mukhtasar Fee Mahaasin Ad-Deen Al-Islaamiy. pages 9-12. slightly paraphrased]