“From that which occurred was: compilation of hadīth, then tafsīr, then the compilation of issues of fiqh (jurisprudence) eminating from pure opinion, and then the compilation of matters related to actions of the heart.
As for the first matter: It was opposed by ‘Umar (), Abu Mūsā al Ash’arī () and a few others whilst the majority allowed it.
As for the second: It was opposed by a group from the Tābiūn such as Imām ash Sha’bī (d.104H) and a small group. Imām Ahmad (d. 241 AH)’s opposition of this intensified.
Also from that which occurred was the compilation of the sayings about Usūl ad Dīn (fundamentals of the Religion). Some embarked to affirm it (ie the attributes of Allāh), whilst others negated it. The extremists amongst the former went to the extent of making tashbīh (resembling Allāh to his creation), whilst the extremists amongst the latter went to the extent of making ta’tīl (denying the attributes of Allāh). The rejection of this from the Salaf such as Imām Abū Hanīfah (d.150H), Qādī Abū Yūsuf (d.182H) and Imām ash Shāfi’ī (d.204H), and their sayings with regards to censuring the people of Kalām (philosophical speech and theology) is well known. The reason for such censure was that the people of ‘Kalām’ spoke about those matters which both the Prophet () and his Companions () remained quiet about. It is established from Imām Mālik (d.179H) that there did not exist at the time of the Prophet () nor that of Abu Bakr () or Umar (), anything from these desires – meaning: the innovation of the Khawārij, the Rāfidah and the Qadarīyah. Indeed, those who came after the first three excellent generations expanded upon matters which the Imāms of the Tābiūn and those who followed them, rejected.
The people of Kalām did not content themselves, until they filled the Dīn with issues and the sayings of the philosophers. They made this philosophy the basis and the fundamental principle to which everything was referred back to, and all that which opposed it from the narrations (of the Prophet (), his Companions ()and the Salaf who followed them) then ta’wīl (false interpretation ) was made of them, even if they were averse to the result. Nor did they content themselves with just this. They claimed that what they had compiled was the noblest branch of knowledge and the most deserving to be acquired; and that those who did not use what they had laid down, then they were from the laymen and the ignorant ones.
So delight is for the one who clings to what the Salaf were upon, and distances himself from the innovations that the khalaf (the latecomers who opposed the aqīdah and manhaj of the Salaf) introduced. However, if one cannot keep away from it, then let him take only that which he needs and let the way of the Salaf be his intended goal.”
[Fath al Barī (13/253) of Ibn Hajar al ‘Asqalānī.]