"Abu'l-ʿAbbās Aḥmad ibn Isḥāq (Arabic: أبو العباس أحمد بن إسحاق; 947/8 – 29 November 1031), better known by his regnal name al-Qādir Bi’llāh (Arabic: القادر بالله, lit. 'Made powerful by God') was the Abbasid caliph in Baghdad from 991 to 1031. He was the grandson of al-Muqtadir, and was chosen in place of the deposed caliph, at-Ta'i, his cousin. His reign was marked by the strengthening of the Abbasid caliphate's role as the champion of Sunni Islam against Shi'ism, notably through the Baghdad Manifesto of 1011, and through the codification, for the first time, of Sunni doctrines and practices in the Risāla al-Qādiriyya, thereby presaging the "Sunni Revival" later in the century." - (en.wikipedia.org 10.10.2021)
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