Musannaf Ibn Abi Shayba 13:2430

Abu Bakr narrated to us, he said: Abu Usama narrated to us, from Uthman ibn Ghiyath, he said: Al-Hasan was asked about a man who leaves his riding beast in a desolate land, and a man takes it and tends to it until he restores it. He said: "It belongs to the one who revived it."