Musnad Ahmad 3575
Musnad of Abdullah bin Mas'ood
It was narrated that Ibn Mas'ood (رضي الله عنه) said: I was tending some sheep belonging to 'Uqbah bin Abi Mu'ait when the Messenger of Allah (ﷺ) and Abu Bakr passed by me. He (the Prophet (ﷺ)) said: "O boy, do you have any milk?" I said: Yes, but this is a Trust (i.e., the sheep do not belong to me). He said: “Is there a sheep that has not been impregnated by the ram? I brought a sheep and he wiped its udder and it filled with milk. Then he milked it into a vessel and drank, and he gave some to Abu Bakr to drink. Then he said to the udder: "Dry up,” and it did. Then I came to him after that and said: O Messenger of Allah, teach me some of these words. He patted me on the head and said: "May Allah have mercy on you; you are a little boy and you will learn (later)."