Musnad Ahmad 652:62

Hassan and Bahz—the meaning is the same—narrated to us, saying: Hammad ibn Salamah narrated to us, from Simak ibn Harb, from al-Nu'man ibn Bashir, who said—I think he attributed it to the Messenger of Allah (peace and blessings of Allah be upon him)—he said: "A man traveled in a desolate land—Hassan said in his narration: meaning a desert—and he said: [He rested] under a tree, and with him was his riding beast, and upon it was his water skin and his food. He woke up and did not see it. He climbed a hill, but did not see it. Then he climbed another hill, but did not see it. Then he turned around, and suddenly it was there, dragging its rein. He was not more joyful for it than Allah is for the repentance of His servant when he repents." Bahz said: "His servant when he repents to Him." Bahz said: Hammad said: I think he attributed it to the Prophet (peace and blessings of Allah be upon him).