Sayyiduna Abu Umamah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) sent me to my people. I reached them in a state of hunger, and found them eating blood. I said: I have come only to forbid you from this. Then I laid down my head (to sleep), and I stood up in a state of weakness. Then someone came to me in my dream with a vessel containing a drink, and said: Take this and drink. Then my stomach became full and I was satiated, then my thirst was quenched. Then I heard them saying: A man from among the chiefs of your people came to you, and you did not even offer him hospitality with (watered-down) milk. So they brought me their thin milk, and I said: I have no need of it; Allah has fed me and given me drink. And I showed them my stomach, and they all, to the last of them, accepted Islam.
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 8042