Musnad Ahmad 32:1422

Hashim narrated to us, Abd al-Aziz narrated to us, from Ishaq ibn Abdullah ibn Abi Talha, from Anas ibn Malik, who said: The Prophet (peace and blessings of Allah be upon him) used to enter the house of Umm Sulaym and sleep on her bed, while she was not in her house. He said: So he came one day, and it was said to her: "This is the Prophet (peace and blessings of Allah be upon him) sleeping on your bed." She said: So I came, and that was in the summer, and the Prophet (peace and blessings of Allah be upon him) was sweating, until his sweat pooled on a piece of leather on the bed. So I began to blot up that sweat and squeeze it into a bottle. He was startled while I was doing that, and he said: "What are you doing, O Umm Sulaym?" I said: "O Messenger of Allah, we hope for its blessing for our children." He said: "You have done right."