context: In the old days, the Arabs lived on the Arabian Peninsula, divided into several competing tribes. In the early 600s, the Prophet Muhammad united a large number of tribes into an Islamic religion. Muhammad's father-in-law, Abu Bakr, was recognized as a Caliph after him. He sought to unite the Arab tribes and prepare for a military expedition to Byzantium and Persia. However, before his death, Kalifina Abu Bakr was only two years old.
question: Who united the Arabs?
answers.text: Prophet Muhammad