What is the meaning of the the title "al-Murtada" by which our master Ali ibn Abi Talib - may Allah be pleased with him - was known, and why was he given this title?

The title "Al-Murtada" was not among the well-known titles of our master Ali ibn Abi Talib, may Allah be pleased with him. It has only been found in the book "Al-Fiqh Al-Akbar" attributed to Abu Hanifa. The meaning of "Al-Murtada" is "the chosen one." Among his most famous titles is "Haydara," and among his kunyas are "Abu Al-Hasan" and "Abu Turab," which was the most beloved kunya to him because the Prophet, peace and blessings be upon him, was the one who bestowed it upon him.