Musnad Ahmad 32:2115

Affan narrated to us, Hammad narrated to us, from Thabit, from Anas, that when the Prophet, peace and blessings of Allah be upon him, intended to shave his head at Mina, Abu Talha took the side of his head, and the barber shaved it. He brought it to Umm Sulaym, and Umm Sulaym used to put it into her perfume. He used to come and take a midday nap at her place on a leather mat, and he was a man who perspired profusely. One day he came, and she began to wipe up the sweat and put it into a bottle of hers. The Prophet, peace and blessings of Allah be upon him, woke up and said, "What are you doing, O Umm Sulaym?" She said, "O Prophet of Allah, it is your sweat; I want to mix it into my perfume."