Abu al-Qasim ibn Muhammad ibn Husayn al-Shafi’i says...
Abu al-Qasim ibn Muhammad ibn Husayn al-Shafi’i says: The copies of Muwatta’ known to be compiled by Malik are eleven, with their denotation being identical and only four of which are commonly referred to, being: Muwatta’ Yahya ibn Yahya, Muwatta’ Ibn Bakr, Muwatta’ Abi Mus’ab and Muwatta’ Ibn Wahb, with diminishing of reference to other copies.
Among the narrations there is great incongruity including bringing forward and backward, addition and omission, the greatest and most ample of which being the additions of the narration of Abu Mus’ab. 554 Ibn Hazm said: In Abu Mus’ab’s narration there is addition exceeding all other Muwatta’s with about one hundred traditions. Al-Suyuti says: In the narration of Muhammad ibn al-Hasan there are several traditions exceeding other narrations of Muwatta’. Dr.
Ahmad Amin has explained the reason of this divergence saying: “Malik used to keep on compiling a copy of his book, but rather he was perpetually changing and modifying in it, and he used to review and revise the traditions, with eliminating whatever could not be confirmed. Those who heard al-Muwatta’ had in fact heard it in different times, with divergence in wording in every copy.
Of these copies extant is the copy narrated by Yahya ibn al-Laythi, which was exposed by al-Zarqani, and the one narrated by Muhammad ibn al-Hasan al-Shaybani, companion of Abu Hanifah, which contained many things that were not found in the copy of Yahya, as he used to mix what he narrated from Malik with his opinions, saying “Often: Muhammad said.” 555 Cause and Time of Its Compilation: 556 Al-Muwatta’ was compiled during the last days of the reign of al-Mansur, in the year 148H.
The reason for this — as reported by al-Shafi’i — was that Abu Ja’far al-Mansur sent after Malik on his coming to al-Madinah, saying to him: Disagreement found way among people of Iraq, so you are asked to compile a book upon which you gather and unite them, hence he compiled al-Muwatta’. In another narration, he said to him also: In it (book) you should avoid oddities of Ibn Abbas, intensities of Ibn Umar and permissions of Ibn Mas’ud.
Malik said to him: O Amir al-Mu’minin it is not for us to compel people to follow and adhere to utterance of one man liable to err and be correct. And, as stated before, al-Mansur was so much concerned with hadith and studying it.