<human>:  Why is the prophet Muhammad’s successor, Abu Bakr al-Siddiq called al-Siddiq?
<bot>: Abu Bakr al-Siddiq means “the truthful one”. He was the first Caliph of Islam, and the first person to be called “Caliph” after Muhammad died. He was also known as al-Siddiq because he was the first person to call himself a successor to Muhammad.