The ceremony, broadcast on state television, was held in Al-Akram mosque in the capital's western district of Mazzeh.
Assad was shown next to Religious Affairs Minister Mohammed Abdel Sattar Sayyed and the mufti of Syria, Ahmad Badredin Hassoun.
Last Friday, the president and his wife Asma also made a pre-Christmas visit to a church in an eastern suburb of Damascus often targeted by rebel artillery.
Assad, a member of the Alawite sector of Shia Islam, presents himself as a protector of Syria's minorities.
He says his secular regime is an example of tolerance, in contrast to the extremism of jihadists such as the Islamic State group which has seized large swathes of the war-torn country.