Large crowds of mourners, clad in black, have assembled outside Tehran's Grand Mosalla to pay their respects to Iran's late supreme leader, Ayatollah Ali Khamenei. His body is currently on display at the mosque, a prelude to his eventual burial in Mashhad next Thursday. Over the coming days, authorities anticipate 15-20 million people attending ceremonies across Iran and Iraq, marking more than four months since Khamenei's death in US and Israeli strikes. The crowds included supporters of the Islamic regime who chanted anti-US slogans and called for revenge for the ayatollah's demise. A 37-year-old professor expressed his sentiments, "We promised the supreme leader we would stand by him till the end." Arash Rahimi, a 40-year-old individual, stated, "Everyone here has come to avenge the blood of their supreme leader. Our relations with the United States will never be good." Khamenei's body will remain in the Grand Mosalla for three days, accompanied by family members also killed in the air strikes. Following this, there will be additional events outside Tehran, with his remains moving to Qom and Najaf, Iraq, before being buried at the Imam Reza Shrine in Mashhad on Thursday. Commemorative events will continue across Iran for the following 40 days, ending on the first anniversary of Khamenei's burial. Ayatollah Khamenei was succeeded as Iran's supreme leader by his son, Mojtaba, who has not been seen in public since assuming the role, fueling speculation about his health. Whether he will attend the funeral remains uncertain, adding intrigue to the meticulously planned ceremony.