Musnad Abu Ya'la al-Mawsili 42:329

Zuhayr narrated to us, Yazid narrated to us, Fudayl ibn Marzuq informed us, from Atiyyah, from Abu Sa’id al-Khudri, from the Prophet (peace be upon him), who said: "Allah is more joyful at the repentance of His servant than a man who lost his riding beast in a desolate land, so he searched for it but could not find it. He then laid down to die. While he was in that state, he heard the sound of his riding beast as it knelt down. He uncovered his face, and there was his riding beast."