Abdullah ibn Umar () (ca.614-693) was the son of the second Caliph Umar ibn Khattab. He was a prominent authority in Hadith and law, and was known for his neutrality toward factions engaged in the first civil war within the Muslim community (656-661).
Muhammad's era — 614 to 632
Muhammad proclaimed his prophethood in 610.
Abd-Allah ibn Umar was born to Umar ibn al-Khattab and his wife Zainab bint Mazaun Jamiah sometime around 614.
Prior to his conversion to Islam, Umar had three wives, however, after he became Muslim only Zainab joined her husband in accepting the new faith. Abdullah also accepted Islam at a young age, but he was not allowed to join Muhammad(Sallallaahu alaihi wa sallam) in battle until he was fifteen. The first battle he fought in was against the forces of Abu Sufyan during the Battle of the Trench, which occurred during 627.
It was recorded from Salim ibn Abd-Allah, from his father, that Muhammad said to his father, "Abdullah would be a good man if he would pray the tahajjud prayers (late night prayers)." Salim said: "After that, 'Abdullah would not sleep during the night save for a small amount at a time." Abdullah was 18 at the end of Muhammad's life in 632.
Abu Bakr's era — 632 to 634
Umar's era — 634 to 644
Uthman's era — 644 to 656
Ali's era — 656 to 661
When Ali became Caliph, Ibn Umar refused to give him allegiance. Instead he moved from Medina to Mecca, saying he was going to perform Umrah (pilgrimage to Mecca at a time other than Hajj).
After the assassination of Caliph Ali ibn Abi Talib, Ibn Umar regretted having let the Caliph fend for himself in the dangerous political environment that had become prevalent.
Muawiya's era — 661 to 680
When Muawiya ibn Abi Sufyan claimed Caliph in 661, Ibn Umar immediately gave him his allegiance.
Yazid's era — 680 to 683
When the people of Medina dethroned Yazid bin Muawiya in 683, Ibn 'Umar gathered his special friends and children and said, "I heard [Muhammad] saying, 'A flag will be fixed for every betrayer on the Day of Resurrection,' and we have given the oath of allegiance to this person (Yazid) in accordance with the conditions enjoined by Allah and His Apostle and I do not know of anything more faithless than fighting a person who has been given the oath of allegiance in accordance with the conditions enjoined by Allah and His Apostle , and if ever I learn that any person among you has agreed to dethrone Yazid, by giving the oath of allegiance (to somebody else) then there will be separation between him and me."
He was a strong proponent of Qadr (doctrine)
He had a number of sons, including Abd-al-Rahman ibn Abd-Allah and Salim ibn Abd-Allah. It is also worth noting that Abdullah's sister, Hafsa bint Umar, was a wife of Muhammad.
Shi'a have a negative view of him, among things for downplaying Ali's role during Muhammad's time and giving support to Yazid ibn Muawiyah ibn Abi Sufyaan, the murderer of the grandson of Muhammed, Hussain ibn Ali and 72 members of his family and companions.