Musnad Ahmad 540:0

Narrated by Abd al-Rahman ibn Hasana: The Prophet (ﷺ) went out, and I followed him. He entered a garden of date palms and sat down. He then covered himself with a garment or a piece of cloth. I approached him and covered him with it. He then stood up and relieved himself. Then he said: "Bring me some water." I brought him a vessel of water. He performed ablution, wiped over his leather socks, and prayed.