Amr bin Maymun said: When Umar (may Allah be pleased with him) was wounded, he began to give his instructions to the members of the Shura: "If the caliphate comes to Sa'd, then that is well; otherwise, whoever becomes caliph should seek his help, for I did not remove him from office because of incompetence or betrayal."
Hadith Referenceالمعجم الكبير للطبراني / العشرة / 318