Musnad Abu Ya'la al-Mawsili 42:344

Zuhayr narrated to us, Affan narrated to us, Hammam narrated to us, al-Mu'alla ibn Ziyad informed us, al-'Ala'—a man from Muzaynah—narrated to me, from Abu al-Siddiq al-Naji, from Abu Sa'id al-Khudri, that they were sitting, reciting and supplicating. He said: The Messenger of Allah (may Allah bless him and grant him peace) came out to them. He said: When we saw him, we fell silent. He said: "Were you not doing such and such?" We said: "Yes." He said: "Then do as you were doing." He sat with us, then said: "Rejoice, O destitute ones of the Emigrants, with success on the Day of Resurrection over the wealthy by five hundred years, until the wealthy person wishes that he had been poor or needy in the world."