Musannaf Ibn Abi Shayba 13:2343

Abu Bakr narrated to us, he said: Affan narrated to us, he said: Hammad ibn Salamah narrated to us, from Asim ibn Bahdalah, from Zirr ibn Hubaysh, from Abdullah, who said: I was a young, adolescent boy grazing sheep for Uqbah ibn Abi Mu'ayt. The Prophet, peace and blessings of Allah be upon him, and Abu Bakr came, having fled from the polytheists. They said, "O boy, do you have any milk to give us to drink?" I said, "I am a trustee, and I will not give you to drink." The Prophet, peace and blessings of Allah be upon him, said, "Do you have a young ewe that the ram has not yet mounted?" I said, "Yes." I brought it to them. The Messenger of Allah, peace and blessings of Allah be upon him, restrained it, wiped the udder, and supplicated. The udder filled with milk. Then he brought a hollowed-out rock and milked into it. He drank, Abu Bakr drank, and I drank. Then he said to the udder, "Shrink," and it shrank.