The Martyrdom of Imam Reza is observed in Iran every year on the 29th or 30th day of the Islamic month of Safar. This public holiday commemorates Ali al-Ridha, the eighth Shia Imam, who was the son of Musa al-Kadhim and a descendant of Prophet Muhammad. Imam Reza was appointed as the successor by the Abbasid caliph al-Ma'mun, but his growing popularity led to his poisoning in 818, as believed by most Shia Muslims. He was buried in a village in Khorasan Province, which is now known as Masshad, meaning "the place of martyrdom," and is Iran's second most populous city. The Imam Reza Shrine in Masshad attracts millions of pilgrims annually, reflecting the significance of this holiday within the Shia community.