He is the author of the work entitled al-ʾIbāna. His kunyah is Abū'l-Qāsim. His lineage is as follows: ʿAbdurraḥmān b. Muḥammad b. Aḥmad b. Forān al-Forānī al-Marwazī. He is among the Shāfiʿī imams. He is the musannif (author) of the work al-ʾIbāna, which contains rare transmissions. However, this book includes unique statements and narrations. He possessed extensive knowledge of uṣūl al-fiqh (principles of Islamic jurisprudence) and furūʿāt (branches of jurisprudence). He learned fiqh from Kaffāl. He went to study with Imām al-Harāmayn at a young age, but Imām al-Harāmayn did not show much favor to him. In al-Nihāya, he saw many errors in him. He was resentful towards him.
Ḥalḥakān said: Whenever Imām al-Harāmayn mentioned the book al-Nihāya, he would say: "Some musannifīn said thus, but erred in this matter." By this, he was actually referring to Abū'l-Qāsim al-Forānī and intended to criticize him.
He died in the month of Ramaḍān in the year 7^, at the age of seventy-three, in the city of Marw. His student Abū Saʿd ʿAbdurraḥmān b. Muḥammad al-Maʾmūn wrote a sharḥ (commentary) on the book al-ʾIbāna and named it Tatmīm al-Bāgh. This student taught in the Madrasa of Ibn Sabʿ and in the Zamāwiyya Madrasa after Abū Isḥāq. He had written this sharḥ up to the section of al-Qud and died before completing it.
Then ʿIsāʿad al-Jilī and others completed it. However, they could not write as scholarly as he did. They did not even come close, and they named their work Tatmimat al-Tatmīm.