Musnad Abu Ya'la al-Mawsili 3:364

Zuhayr narrated to us, Waki' narrated to us, from Yunus bin Abi Ishaq, from al-Sha'bi, from Ali, who said: I was with the Prophet, may Allah bless him and grant him peace, when Abu Bakr and Umar approached. He said: "These two are the masters of the middle-aged people of Paradise, from the first and the last, except for the Prophets and the Messengers."