Musnad Abu Ya'la al-Mawsili 10:5

Ibrahim ibn al-Hajjaj al-Sami narrated to us, Hammad narrated to us, from Ali ibn Zayd, from Abu al-Tufayl, from the Prophet (peace be upon him), and from Habib and Humayd, from al-Hasan, that the Messenger of Allah (peace be upon him) said: "While I was drawing water tonight, black sheep and dust-colored sheep came to me. Then Abu Bakr came and drew a bucket or two, and there was weakness in them, and may Allah forgive him. Then Umar came, and it (the bucket) transformed into a large bucket, so he filled the basins and quenched the thirst of those who came. I have not seen a genius among the people who was better at drawing water than him." I interpreted the black sheep as the Arabs, and the dust-colored ones as the non-Arabs.