Abdullah B Umar (d-73H) عبدالله بن عمر
Son of the famous second `caliph Umar. Although still very young, he became a Muslim and migrated with his father to Madinah. He took part in the famous Yarmuk battle as well as in the conquest of Egypt. He also participated in two African expeditions. A devoted Muslim, he was not only the most knowledgeable of the Sunnah of the Prophet but also the most ardent of its followers. Sometimes the scholars consider it enough to cite his practice as proof of the Prophet's Sunnah. When the Prophet (saws) prayed inside the Ka’bah at the fall of Makkah, it was Ibn `Umar who was the first to rush forward to enquire with Bilal about the exact spot where the Prophet had prayed. It is said that when he travelled, he camped at places where the Prophet had camped and went to the spots where the Prophet had gone to relieve himself. `Umar was requested by the people during his life-time to nominate his son`Abdullah for Khilafah, but he refused. At `Uthman's martyrdom people again requested him to take charge of the Khilafah, but he refused. He died in 73 H.
The Musnad of Ahmad has 2039 reports coming through him.