Musnad Ahmad 32:60

'Abd al-Wahhab ibn 'Abd al-Majid narrated to us, from Ayyub, from Anas ibn Sirin, from Anas ibn Malik, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) used to enter upon Umm Sulaym, and she would spread out a leather mat for him, and he would take a midday nap upon it. She would take some of his sweat and put it into her perfume. And she would spread out a *khumra* (a small prayer mat made of palm leaves) for him, and he would pray upon it."