Musnad Ahmad 33:224

Hashim ibn al-Qasim and Hasan ibn Musa narrated to us, they said: Zuhayr narrated to us, Abu al-Zubayr narrated to us, from Jabir, who said: The Messenger of Allah (peace and blessings of Allah be upon him) sent us and appointed Abu Ubaydah as our commander to intercept a caravan of Quraysh. He provided us with a leather bag of dates, as he found nothing else for us. He said: Abu Ubaydah would give us one date at a time. I said: How did you manage with it? He said: We would suck on it as a child sucks, then drink water over it, and it would suffice us for our day until night. He said: We would strike the leaves of trees with our sticks, then moisten them with water and eat them. He said: We set off along the seashore, and there appeared to us on the shore something like a huge sand dune. We approached it, and it was a beast called al-Anbar (ambergris/whale). Abu Ubaydah said: "It is carrion." Then he said: "No, rather we are the messengers of the Messenger of Allah (peace and blessings of Allah be upon him) and in the path of Allah, and you are in a state of necessity, so eat." We stayed there for a month, and we were three hundred, until we became fat. I saw us scooping out oil from the hollow of its eye with buckets, and cutting from it pieces of meat like a bull—or like the size of a bull. He said: Abu Ubaydah took thirteen men and seated them in the hollow of its eye. He took one of its ribs and stood it upright, then he saddled the largest camel we had—Hasan said: Then he saddled the largest camel that was with us—and it passed underneath it. We took a supply of its meat as dried strips. When we arrived in Medina, we came to the Messenger of Allah (peace and blessings of Allah be upon him) and mentioned that to him. He said: "It is a provision that Allah brought out for you. Do you have any of its meat with you so that you may feed us?" He said: So we sent some of it to the Messenger of Allah (peace and blessings of Allah be upon him), and he ate it.