His worldly success was something of a mixed blessing, and in mid-career, after considerable reflection, he was gripped by an intense fear for his soul and his fate in the afterlife, and he resigned from his post, travelling first to Jerusalem and then to Damascus to purify his heart by following the way of Sufism. In Damascus, he lived in seclusion for some ten years, engaged in spiritual struggle and the remembrance of Allah, at the end of which he emerged to produce his masterpiece lhya’ ‘ulum aI-din [Giving life to the religious sciences], a classic among the books of the Muslims about internalising god fearingness (taqwa) in one’s dealings with Allah, illuminating the soul through obedience to Him, and the levels of believers’ attainments therein. The work shows how deeply Ghazali personally realised what he wrote about, and his masterly treatment of hundreds of questions dealing with the inner life that no one had previously discussed or solved is a performance of sustained excellence that shows its author’s well-disciplined legal intellect and profound appreciation of human psychology. He also wrote nearly two hundred other works on the theory of government, Sacred Law, refutations of philosophers, tenets of faith, Sufism, Koranic exegesis, scholastic theology, and bases of Islamic jurisprudence. He died in Tabiran in 505/1111 (al-A ‘lam (y136), 7.22; lhya’ ‘ulum ai-din (y39), 1.330; al-Munqidh min al-dalal (y41), 46-50; al-Shita (y116), 2.602;N; and n).

(Keller, Nuh Ha Mim. Reliance of the Traveller: A Classic Manual of Islamic Sacred Law. Rev. ed. Beltsville, MD: Amman, 1996) https://en.wikipedia.org/wiki/Al-Ghazali