Sunan Ibn Majah, Chapter: The Book of the Sunnah

"I heard Ibn Abbas say: 'When Umar was placed on his bed (i.e., his bier), the people gathered around him, praying and invoking blessings upon him,' or he said, 'praising him and invoking blessings upon him before (the bier) was lifted up, and I was among them. No one alarmed me except a man who crowded against me and seized me by the shoulder. I turned and saw that it was 'Ali bin Abu Talib. He prayed for mercy for 'Umar, then he said: "You have not left behind anyone who it is more beloved to me to meet Allah with the like of his deeds than yourself. By Allah, I think that Allah will most certainly unite you with your two companions, and that is because I often heard the Messenger of Allah (saw) saying: 'Abu Bakr, 'Umar and I went; Abu Bakr, 'Umar and I came in; Abu Bakr, 'Umar and I went out.' So I think that Allah will most certainly join you to your two companions." (Sahih)