Musnad Abu Ya'la al-Mawsili 41:26

Mus'ab al-Zubayri narrated to us, al-Dahhak bin Uthman narrated to us, from Abd al-Rahman bin Abi al-Zinad, from Hisham bin Urwah, from his father, from Sa'id bin Zayd, who said: I and Umar bin al-Khattab asked the Messenger of Allah, may Allah bless him and grant him peace, about Zayd bin Amr. He said: "He will come on the Day of Resurrection as a nation by himself."