Musnad Ahmad 5:335

'Ali ibn Ishaq narrated to us, 'Abdullah—meaning Ibn al-Mubarak—informed us, 'Umar ibn Sa'id ibn Abi Husayn informed us, from Ibn Abi Mulaykah, that he heard Ibn 'Abbas saying: 'Umar ibn al-Khattab was placed upon his bier, and the people gathered around him, supplicating and praying before he was lifted, and I was among them. Nothing startled me except a man who had taken hold of my shoulders from behind me. I turned around, and behold, it was 'Ali ibn Abi Talib. He invoked mercy upon 'Umar, then said: "You have not left behind anyone more beloved to me that I would like to meet Allah, the Exalted, with the likes of his deeds than you. And by Allah, I used to think that Allah would surely place you with your two companions. That is because I used to frequently hear the Messenger of Allah, peace and blessings of Allah be upon him, say: 'I went, and Abu Bakr, and 'Umar; and I entered, and Abu Bakr, and 'Umar; and I left, and Abu Bakr, and 'Umar.' And I used to think that Allah would surely place you with them both."