Sultan Suleiman the Magnificent promoted him to Shaykh al-Islām – the supreme judge and highest official – in 1545, an office Ebussuud held until his death and which he brought to the peak of its power.

[6] Ebussuud also issued legal rulings (fatwās) which labeled the Qizilbash, regardless of whether they lived on Iranian or Ottoman soil, as "heretics", and declared that killing them would be viewed as praiseworthy, rather than just being allowed according to the law.

[11][12] The chief function of SHaykh al-Islām was to issue fatwās in response to legal questions from the Sultan, his ministers, governors or judges, or from members of the public seeking out-of-court settlements or simply answers to queries.

[14] Ebussuud’s reform of the procedure of composing fatwas allowed the office of SHaykh al-Islām to develop a standardized style of Ottoman fatwā documents and issue large volumes of them in relatively short periods of time.

[11][13] Ebussuud’s fatwās collections, known as Ma‘ruḍāt, have received considerable attention in modern scholarship and were heavily cited and quoted by generations of legal scholars who came after him.

[11] While Ebussuud’s contributions to the Ottoman land and tax codes have garnered great interest in modern historiography, his opinions on those issues occupied a limited space in his fatwas.

[16] Instead, two broadly defined foci in Ebussuud’s fatwās were economic concerns, such as contractual and property-related issues, and religious-doctrinal, communal (including non-Muslims) and family matters.