'Umar ibn al-Khattab

(born c. AD 586, Mecca, Arabian Peninsula—died Nov. 3, 644, Medina) Second Muslim caliph (634–644). He initially opposed the Prophet Muhammad but became a Muslim c. 615. His daughter Hafsah married Muhammad in 625. He was nominated by Abu Bakr as his successor. As caliph he spread Islam to Egypt, Syria, and Persia. His innovations affected taxation, social welfare, and the empire's entire financial and administrative fabric, and he was noted for his justice, social ideals, and candour.

Source: Encyclopedia Britannica