Umar ibn Khattab: During Muhammad's era. In 610 Muhammad started delivering the message of Islam. Umar, alongside others in Makkah, opposed Islam and threatened to kill Muhammad. He resolved to defend the traditional, polytheistic religion of Arabia. He was most adamant and cruel in opposing Muhammad and very prominent in persecuting the Muslims. Umar was the first man who resolved that Muhammad had to be murdered in order to finish Islam. Umar firmly believed in the unity of the Quraish and saw the new faith of Islam as a cause of division and discord among the Quraish.
Due to the persecution at the hands of the Quraish, Muhammad ordered his followers to migrate to Abyssinia. As a small group of Muslims migrated Umar felt worried about the future unity of the Quraish and decided to have Muhammad assassinated.
Converting to Islam
Umar converted to Islam in 616, one year after the Migration to Abyssinia. The story was recounted in Ibn Ishaq's Sīrah; On the way to murder Muhammad, Umar met his best friend Nu'aim ibn Abdi 'Allah who had secretly been converted to a Muslim but he did not tell Umar anything about it. When Umar told him that he was going to kill Muhammad he was afraid. He knew Umar will attempt what he said. So just to divert his attention he told him to set his own house in order first, as his sister and her husband had converted to Islam. Upon arriving at her house, Umar found his sister and brother-in-law Saeed bin Zaid (Umar's cousin), reciting the verses of the Qur'an(Surah Taha). He started quarreling with his brother-in-law . When his sister came to rescue her husband, he also started quarreling with her. Yet still they kept on saying "you may kill us but we will not give up Islam". Upon hearing these words, Umar slapped his sister so hard that she fell to the ground bleeding from her mouth. When he saw what he did to his sister now, out of guilt he calmed down and asked his sister to give him what she was reciting. She gave him the paper on which was written the verses of the chapter Ta-Ha. He was so struck by the beauty of the verses that he accepted Islam that day. He then went to Muhammad with the same sword he intended to kill him with and accepted Islam in front of him and his companions. Umar was 27 when he accepted Islam. Following his conversion, Umar went to inform the chief of Quraish, Amr ibn Hishām, about his acceptance of Islam. According to one account, Umar thereafter openly prayed at the Kaaba as the Quraish chiefs, Amr ibn Hishām and Abu Sufyan ibn Harb, reportedly watched in anger. This further helped the Muslims to gain confidence in practicing Islam openly. At this stage Umar even challenged anyone who dared to stop the Muslims from praying, although no one dared to interfere with Umar when he was openly praying.
Umar’s conversion to Islam gave power to the Muslims and the faith in Mecca. It was after this that Muslims offered prayers openly in Masjid al-Haram for the first time. Abdullah bin Masoud said:
Umar's embracing Islam was our victory, his migration to Medina was our success and his reign a blessing from Allah, we didn't offer prayers in Al-Haram Mosque until Umar accepted Islam, when he accepted Islam Quraish were compelled to let us pray in the Mosque.
All these things earned Umar the title of Farooq, meaning he who distinguishes truth from falsehood.
Umar's Title of Al Farooq
Mujahid, on the authority of Ibn Abbas related that he had asked 'Umar bin Al-Khattab why he had been given the epithet of Al-Farooq (he who distinguishes truth from falsehood), he replied: After I had embraced Islam, I asked the Prophet : 'Aren't we on the right path here and Hereafter?' The Prophet answered: 'Of course you are! I swear by Allâh in Whose Hand my soul is, that you are right in this world and in the hereafter.' I, therefore, asked the Prophet 'Why we then had to conduct clandestine activism. I swear by Allâh Who has sent you with the Truth, that we will leave our concealment and proclaim our noble cause publicly.' We then went out in two groups, Hamzah leading one and I the other. We headed for the Mosque in broad daylight. When the polytheists of Quraish saw us, their faces went pale and got incredibly depressed and resentful. On that very occasion, the Prophet attached to me the epithet of Al-Farooq."
Migration to Medina
In 622 due to the growing popularity of Islam in the city of Yathrib (later renamed Al-Medīna Al-Munawara, the enlightened city, or simply Medina) Muhammad ordered his followers to migrate to Medina. Muslims usually migrated at night due to fear of Quraish's resistance to that migration, but Umar is reported to have migrated openly during the day time. Ibn AsakirAli said: I don’t know of anyone who didn’t emigrate in secret except for Umar ibn al-Khattab; because when he wanted to emigrate he strapped on his sword, put his bow over his shoulder, carried his arrows in his hand, and came to the Ka‘bah where the nobles of Quraysh were in the courtyard. He performed seven circuits, and then prayed two raka‘at at the Station (of Ibrahim). Then he approached their circle one step at a time and said, Whoever wishes to bereave his mother, orphan his children and widow his wife then let him meet me behind this valley.” Not one of them followed him. Umar migrated to Medina accompanied by his cousin and brother-in-law Saeed ibn Zaid. narrated that
Life in Medina
Medina became the new center of Islam and the religion spread rapidly across Arabia. When Muhammad arrived in Medina, he paired off each immigrant (Muhajir) with one of the residents of the city (Ansari), joining Muhammad ibn Maslamah with Umar making them brothers in faith. Later in Umar's reign as caliph Muhammad ibn Muslamah would be assigned the office of chief inspector of Accountability. Muslims remained in peace in Medina for approximately a year before the Quraish raised an army to attack them. In 624 Umar participated in the first Battle between Muslims and Quraish of Mecca i.e. Battle of Badr.In 625 he participated in the Battle of Uhud. In the second phase of Battle when Khalid ibn Walid's Cavalry attacked Muslims at the rear changing the victory of Muslims to defeat, rumors of Muhammad’s death were spread many Muslim were warriors routed from the battle field, Umar too was initially routed but hearing that Muhammad was still alive he went to Muhammad at the mountain of Uhud and prepared for the defenses of the hill to keep the Quraishi army down the hill. Later in the year Umar was a part of campaign against the Jewish tribe of Banu Nadir. In 625 Umar’s daughter Hafsah was married to Muhammad.
Later in 627 he participated in the Battle of the Trench and also in the Battle of Banu Qurayza. In 628 Umar participated in the Treaty of Hudaybiyyah and was made one of the witness over the pact. In 628 he was a part of Muslims' campaign to Khaybar. In 629 Muhammad sent Amr ibn al-A’as to Zaat-ul-Sallasal from where he called for reinforcement and Muhammad sent Abu Ubaidah ibn al-Jarrah with reinforcement, serving under him were Abu Bakr and Umar, they attacked and defeated the enemy. In 630 when Muslim armies rushed for the Conquest of Mecca he was part of that army. Later in 630 he was part of Battle of Hunayn and Siege of Ta'if. He was part of Muslim's army that went for the campaign of Tabuk under Muhammad's command and he was reported to have given half of his wealth for the preparation of this expedition. He also participated in a farewell Hajj of Muhammad in 631.
Death of Muhammad
Muhammad died on 8 June 632. Just before the death, there were a group of companions of Muhammad were near him when Muhammad asks that he want to write a will and hence require a pen and paper. Umar said that Muhammad is seriously ill and his brain is not working fully. Abu bakar also agreed on that. When Muhammad heard that, he ordered both to leave the room. Umar was full of grief upon hearing the news, Umar, the devoted disciple, could not accept the reality that the "Messenger of God" has died. According to the Qur'an, "Muhammad is but a messenger; messengers have passed away before", i.e. died or killed. It is said that Umar promised to strike the head of any man who would say that Muhammad died. At this point Abu Bakr is reported to have come out to the Muslim community and gave his famous speech which included:
"Whoever worshipped Muhammad, let them know that Muhammad is dead, and whoever worshipped God, let them know that God is alive and never dies."
Abū Bakr then recited these verses from the Qur'an:
"Muhammad is but a messenger; messengers (the like of whom) have passed away before him. If, then, he dies or is killed, will you turn back on your heel?".
Hearing this from Abu Bakr, the most senior disciple of Muhammad, Umar then fell down on his knees in great sense of sorrow and acceptance of the reality. Sunni Muslims say that this denial of Muhammad's death was occasioned by his deep love for him.