Amr bin Hurayth (may Allah be pleased with him) said: Ali (may Allah be pleased with him) was sitting on the pulpit when he mentioned Abu Bakr and Umar (may Allah be pleased with them both) and said: "The best person of this Ummah after its Prophet (peace and blessings be upon him) is Abu Bakr, and the second is Umar; and if I wished to mention the third, I would do so."
Hadith Referenceالمعجم الكبير للطبراني / العشرة / 177