It is narrated from Sayyiduna Abdullah bin Ukaym (may Allah be pleased with him): A letter of the Messenger of Allah (peace and blessings be upon him) was read out to us in the land of Juhaynah, when I was a young man, and it was written in it: "Do not make use of the skin of a dead animal, nor of its sinews."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 42