Shortly after he defeated Sonny Liston for the world heavyweight championship in February 1964, Muhammad Ali announced that he had joined the Nation of Islam. Here Ali meets with Malcolm X, who led Ali to the Nation of Islam, in New York.
John Peodincuk/NY Daily News Archive/Getty Images
Flanked by fellow pilgrims, Muhammad Ali prays inside the Holy Mosque in Mecca during a January 1972 pilgrimage to the spiritual center of the Muslim world. After visiting the Prophet Mohammed's tomb in Medina, Ali said he became convinced that he could defeat Joe Frazier in a rematch.
Bettmann Archive/Getty Images
Muhammad Ali kisses the Holy Black Stone in the Kaaba during his pilgrimage to Mecca in January 1972. The stone is said to have been given to Abraham by the archangel Gabriel.
Bettmann Archive/Getty Images
Ali addresses a Nation of Islam meeting in London in December 1974. The following year, Ali left the Nation of Islam and embraced Sunnism, a more mainstream Islamic faith.
Tim Graham/Evening Standard/Getty Images
Muslims reach out to shake hands with Muhammad Ali during his visit to a mosque in Kuala Lumpur, Malaysia, in June 1975. After leaving the Nation of Islam, Ali followed Sunni Islam.
TEE/AP
Ali prays at a mosque in Cairo in October 1986.
MIKE NELSON/AFP/Getty Images
Muhammad Ali prays in a mosque at his former training camp in Deer Lake, Pennsylvaina, in June 1991. By 2005, Ali had embraced Sufism, a strand of Islam that emphasizes a personal connection with the divine.
RICHARD DREW/AP
After the attacks of 9/11, Muhammad Ali spoke out against terrorism, saying that true followers of Islam are peaceful.