Ibn Khaldūn (رحمه الله) stated, “And he enjoyed leadership status and a solid foothold in his traversal of the Ashʿarī path as he was the one who introduced it to the people of al-Maghrib as we previously mentioned.”

Shihāb al-Dīn al-Salāwī al-Mālikī affirms the statements of Ibn Khaldūn in his history book, Tārīkh al-Salāwī: al-Istiqṣā li Akhbār Duwal al-Maghrib al-Aqṣá. He further mentions about Ibn Tūmart, “And he would censure the people due to their adherence to the madhhab of the Salaf (first three generations of Muslims) and their affirmation of Allāh’s Attributes as they have come in the texts (i.e. according to their apparent linguistic meanings). Due to this fact, he would make takfīr of them according to one of the two opinions of the Ashʿarīs concerning takfīr. It was also because of this fact that he named his sect ‘al-Muwaḥḥidīn’ (the people of al-Tawḥīd, i.e. the people upon the Oneness of Allāh [monotheism]) as an indication that whoever differed with them was not a Muwaḥḥid. Thus, many people were deceived by him and from that time on, the belief of the Ashʿarīs appeared in the Islamic lands of al-Maghrib.”

1 The methodology of Takfīr is the unlegislated deeming of other Muslims as being non-Muslim initially introduced by the Khawārij for those who committed major sins and later adopted by various deviant sects concerning those who differed with them in issues of creed or ʿAqīdah.
2  Tārīkh Ibn Khaldūn entitled, Al-ʿIbr wa Dīwān al-Mubtada wal-Khabr fī Ayām al-ʿArab wal-ʿAjam wal-Berber wa man ʿĀsarahum min Dhawī al-Sultān al-Akbar, (pg.117, v.1)
3 Al-Salāwī’s statement was abridged in Al-Risālatu al-Mūʾjizah fī Bayān Barāʾatu al-Imām Mālik wa Aṣḥābuhu wa Kibār Atbāʿihi min Madhab al-Ashāʿirah, (pg. 8), Tārīkh al-Salāwī: al-Istiqṣā li Akhbār Duwal al-Maghrib al-Aqṣá, (pg.73, v.2)