In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Indeed, Allaah severely censured the one who does not act [upon knowledge he has acquired]. Allaah said:
وَاتْلُ عَلَيْهِمْ نَبَأَ الَّذِي آتَيْنَاهُ آيَاتِنَا فَانسَلَخَ مِنْهَا فَأَتْبَعَهُ الشَّيْطَانُ فَكَانَ مِنَ الْغَاوِينَ
وَلَوْ شِئْنَا لَرَفَعْنَاهُ بِهَا وَلَٰكِنَّهُ أَخْلَدَ إِلَى الْأَرْضِ وَاتَّبَعَ هَوَاهُ ۚ فَمَثَلُهُ كَمَثَلِ الْكَلْبِ إِن تَحْمِلْ عَلَيْهِ يَلْهَثْ أَوْ تَتْرُكْهُ يَلْهَث ۚ
And recite [O Muhammad] to them the story of him to whom We gave Our Aayaat [proofs, evidences, verses, lessons, signs, revelations, etc.], but he threw them away, so Shaitan [satan] followed him up, and he became of those who went astray. And had We willed, We would surely have elevated him therewith but he clung to the earth and followed his own vain desire. So his description is the description of a dog: if you drive him away, he lolls his tongue out, or if you leave him alone, he [still] lolls his tongue out. [Surah Al-A’raaf’ Aayaat 175 – 176]
This person fell into disbelief due to not acting upon [the knowledge he acquired] and due to not honouring the divine revelation. An absence of honouring and applying this knowledge which you have gained and mastered will lead you to Bidah; it might lead you to sinful [immoral behaviour] and it might lead you to kufr. This person [mentioned in Surah Al-A’raaf Aayaat 175-176] was a prominent scholar, but he threw away the knowledge which Allaah entrusted on him due to not acting upon it. Many people do not act upon [the knowledge they have acquired], so he [i.e. the individual] is led towards sinful deeds, because he does not act upon [the knowledge he has acquired]. Allaah said:
كَبُرَ مَقْتًا عِندَ اللَّهِ أَن تَقُولُوا مَا لَا تَفْعَلُونَ
Most hateful it is with Allah that you say that which you do not do.[Surah As-Saff’ Aayah 3]
Allaah’s Aid is sought, [an absence of acting upon the knowledge he has acquired] might lead him to fall into Bidah and misguidance, and maybe that the Bidah he falls into is kufriyyah [Ref 1], or he might fall into kufr straight away – and Allaah’s Aid is sought. [Source: Marhaban Yaa Taalibal Ilm’ page 225. Slightly paraphrased
Ref 1: Bidah Al-Mukaffirah and Bidah al-Mufassiqah
Bidah Al-Mukaffirah: It is the Bidah that is tantamount to disbelief. Al-Allaamah Rabee Bin Haadi Al-Madkhali (may Allaah preserve him) was asked whether there is a difference between Bidah Al-Mukaffirah and Bidah Al-Mufassiqah; so Shaikh said that there is Bidah Mukaffirah, such as rejecting the Ruyah (i.e. denying that the believers will see Allaah in the afterlife); rejecting Allaah’s Uluww [i.e. denying that Allaah is above his creation –Allaah ascended over the Throne in a way that benefits his majesty)]; invoking other than Allaah; offering slaughtered sacrifice (i.e. animals) to other than Allaah etc. These are affairs of Bidah Al-Mukaffirah (the bidah that is tantamount to disbelief).
But we do not make Takfeer of the people who commit this type of Bidah until we establish the proofs against them. That is because some of them (i.e. the people who fall into these affairs) carry doubts and are far away from the era of Prophethood and its light (i.e. guidance). So they fall into the likes these innovations.
Rejecting the Ruyah is disbelief; rejecting Allaah’s Uluww is disbelief; the saying that the Qur’aan is created is disbelief-major disbelief. But this person, -[who testifies that none has the right to be worshipped except Allaah and that Muhammad is the messenger of Allaah, and he prays, observes fasting, wants paradise and believes in that] -received the doubts of the people of falsehood, so he falls into the likes of these affairs (i.e. these innovations that are tantamount to disbelief). So we say to him: You have fallen into disbelief and the evidence is this and this, and we clarify for him. So if Allaah grants him Tawfeeq and he returns to the truth, then all praise is due to Allaah. But if not, we declare him a disbeliever after establishing the proofs against him.
As for Bidah Al-Mufassiqah it is other than this (i.e. it is not at the level of that which is tantamount to disbelief)…. [Abridged and paraphrased, see www.rabee.net/ar/questions.php?cat=26&id=484 ]
On the other hand, who are those qualified to make Takfeer?
Question: O Respected Shaykh, who is the murtadd (apostate)? We hope for you to define it in a clear manner, for sometimes the judgement of apostasy can be made upon a person while there is some doubt that he had.
Shaykh Salih al-Fawzaan: The judgement of apostasy and expelling someone from the religion is only appropriate for the people of knowledge who are firmly grounded in knowledge, and they are the judges in the various Shareeah law courts, and those who are able of giving legal verdicts. And this is just like the other matters, and it is not the right of every person, or from the right of those who are learning, or those who ascribe themselves to knowledge, but who have deficiency in understanding. It is not appropriate for them to make judgements of apostasy (upon others). Since, mischief will arise from this, and sometimes a Muslim might be judged as an apostate but he is not actually so. And the takfir of a Muslim who has not committed one of the nullifications of Islaam contains great danger. Whoever says to his brother O Kaafir or O Faasiq, and he is not like that, then the words will fall back upon the one who said them. Hence, the ones who actually judge with apostasy are the legislative judges and those who are able and fit for giving legal verdicts. And as for those who enforce the judgements they are the leaders of the Muslims (wullaat al-amr). As for whatever is other than this, then it is mere confusion.
Question: Some of the students of knowledge are a bit lax towards applying the word of apostasy (riddah) to a Muslim, and this person might sometimes be asked by the Muslims to carry out the hadd punishment for apostasy when the Sultaan does not carry it out upon the one they consider deserves it, the one who has been judged with apostasy.
Shaykh Salih al-Fawzaan: Meting out the punishments is only appropriate for the leader of the Muslims and it is not for every person to establish the punishment, since confusion, and corruption necessarily follows from this, and also the cutting off of the society, tribulations and provocations occur. Establishing the punishments is appropriate (i.e. befits only) to the Muslim leader. The Prophet (sallallaahu alaihi wasallam) said, Pardon each other for the punishments that are between you, but when the execution of the punishment reaches the [authority of the] Sultaan, then Allaah curses both the one who seeks intercession and the one who grants the intercession [i.e. to revoke the punishment].
And from the responsibilities of the Sultaan in Islaam, and from those matters that befit him is the establishment of the punishments after they have been established legislatively, via the Shareeah law courts, upon the one who fell into the crime for which the legislator has designated a specific punishment, such as for stealing. So what has been said is that establishing the punishments (i.e. meting them out) is from the rights of the Sultaan, and when the Muslims do not have a Sultaan amongst them, then they should just suffice with commanding the good and forbidding the evil, and calling to Allaah, the Might and Majestic, with wisdom, good admonition and arguing with that which is best. And it is not permissible for individuals (in the society) to establish the hudood, since that, as we have mentioned, will bring about chaos, and also provocations, and tribulations will arise, and this contains greater corruption than it contains rectification. And from amongst the Shareeah principles that are submitted to is, Repelling the harmful things takes precedence over bringing about the beneficial things.