Shurayh bin Ubayd, Rashid bin Sa'd and others narrate: When Sayyiduna Umar (may Allah be pleased with him), at the place called Sargh, received the news that a severe epidemic had broken out in Syria, Sayyiduna Umar (may Allah be pleased with him) said: "I have learned that a severe epidemic has broken out in Syria. I had thought that if my death comes while Abu Ubaydah is alive, I will appoint him as my successor; and if Allah Almighty asks me about it: 'Why did you appoint him as caliph over the Ummah of Sayyiduna Muhammad (peace and blessings be upon him)?' I will answer: I heard the Messenger of Allah (peace and blessings be upon him) say: 'Every prophet has a trustee, and my trustee is Abu Ubaydah bin al-Jarrah.'" The people objected to this and said: "What about the high-ranking clan of Quraysh?" The narrator says: By this they meant Banu Fihr. Then Sayyiduna Umar (may Allah be pleased with him) said: "If my death comes when Abu Ubaydah has already passed away, I will appoint Mu'adh bin Jabal as my deputy; and if my Lord asks me why I made him caliph, I will say that I heard the Messenger of Allah (peace and blessings be upon him) say: 'He will be raised on the Day of Resurrection ahead of the scholars as a nabdhah (that is, a step apart, with a distinct and prominent standing).'"
Imam Ahmad recorded this narration.
This narration is mursal; Rashid and Shurayh did not meet the time of Sayyiduna Umar (may Allah be pleased with him).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 14912