Abu al-Qasim (teknonym)
Abu al-Qasim (Arabic: أبو القاسم) is a title of Prophet Muhammad (s). After the birth of Qasim, son of the Messenger of God, he was surnamed Abu al-Qasim. It is reported from al-Shaykh al-Saduq (d. 381 AH) that this teknonym was given for belief and disbelief in the Prophet (s), after which people became divided between paradise and hell. He also says: therefore, the Prophet (s), being the father of Imam Ali (a) and that of other Muslims, is called "Abu al-Qasim" because he divides paradise from hell.
According to Muhammad b. 'Ali Ardabili in Jami' al-Ruwat (book), this teknonym has also been attributed to Imam al-Sajjad (a) and has also been used for Imam al-Mahdi (a). Enayatullah Qahpai, a Shia scholar of the 11th century AH, states that the teknonym Abu al-Qasim was more commonly associated with Imam al-Mahdi (a) than with the Prophet (s). Sheikh al-Hurr al-'Amili, in Wasail al-Shi'a, holds that if someone is named Muhammad, it is discouraged to give him the teknonym Abu al-Qasim. According to a report based on registered names at the Civil Registration Office of Iran, Abu al-Qasim ranked among the top 100 male names in Iran between 1297 and 1380 SH.