Sayyiduna Jabir (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) sent us out, appointing Abu Ubaydah (may Allah be pleased with him) as our commander, so that we could watch over the caravans of Quraysh. We had no provisions except one bag of dates, and Abu Ubaydah (may Allah be pleased with him) would give us only one date each. We asked: What did you do with it? The narrator said: We would suck it as a child sucks, then drink water after it, and that would suffice us for a day. We would beat leaves down with our sticks, soak them in water and eat them. Then we saw on the seashore a fish like a huge sand-dune; its name was al-Anbar. Abu Ubaydah (may Allah be pleased with him) said: It is carrion. Then he said: We are the envoys of the Messenger of Allah (peace and blessings be upon him) in the path of Allah, and we have been compelled by necessity, so eat. We, three hundred people, ate the fish for a month until we grew fat. We would scoop out a jar of oil from the socket of that fish's eye, and cut from it a chunk like a bull. Abu Ubaydah (may Allah be pleased with him) took thirteen men and stood them in the eye socket, and he set up one of its ribs and had a large camel with a saddle on it pass beneath it. We took its meat as provisions for the journey. When we came to Madinah we told the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) said: "It was provision that Allah brought out for you. Do you have any of its meat, so that you may feed us too?" So we sent some of it to the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) ate it.
(b) In the narration of Ahmad bin Yunus: We went along the seashore and saw something like a huge sand-dune; when we came near it, it was the Anbar fish. We would take out a vessel of fat from its eye socket, and we would cut a chunk from it like a bull. The narrator said: They were seated in the socket of that fish's eye. At the end of this hadith it says: We sent its meat to the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) ate it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيد والذبائح / 18962