Umar set out to kill Muhammad and became Islam's second caliph
In Sunni tradition, Umar ibn al-Khattab once took up his sword intending to assassinate Muhammad. A clansman stopped him with news that Umar's own sister had secretly converted. Reading her copy of a Quranic chapter changed his mind, and he later led the conquest of Persia and introduced the Hijri calendar.
Umar was born around 584 in Mecca into the Banu Adi, a minor clan of the Quraysh. As a youth he herded camels for a father he remembered as harsh, but he also learned to read and write, rare skills in pre-Islamic Arabia, loved poetry, and trained in martial arts. When Muhammad began preaching, Umar clung to Qurayshi polytheism and opposed the new faith fiercely.
After his change of heart in 616 he openly declared his faith and became the first Muslim willing to pray publicly at the Kaaba. In 622, when Muslims moved to Yathrib, later Medina, he travelled openly rather than by night. He fought at Uhud, the Trench and Hunayn, joined the pledge under the tree in 628 and the taking of Mecca, and Muhammad called him al-Faruq, the one who distinguishes right from wrong, for his sound judgement.
When Muhammad died on 8 June 632, Umar at first refused to believe it, until Abu Bakr reminded the community that God, not the Prophet, was eternal. Umar then played a central part at the Saqifa gathering that made Abu Bakr caliph, though he later called that hurried agreement no precedent for the future. Scholars disagree about how much pressure he placed on Ali, who believed he should have succeeded Muhammad. Abu Bakr named Umar his successor shortly before dying in 634.
Umar ruled from August 634 and oversaw an unprecedented expansion; campaigns against the Sasanian Empire conquered Persia within two years, from 642 to 644. Jewish tradition credits him with lifting the Christian ban on Jews entering Jerusalem. Sunni Muslims revere him as a model of justice, while Shia Muslims view him negatively. He was assassinated in 644.
Source: Umar
