Musannaf Ibn Abi Shayba 28:1151

Asbat ibn Muhammad narrated to us, from Mutarrif, from Amir, regarding a man who abandoned his riding animal, and another man took it. He said: Its owner came and disputed with him before Amir. He (Amir) said: "This is a matter that was judged before today. If he abandoned it in the middle of a wilderness, he is more entitled to his riding animal. But if he abandoned it in a place of pasture and security, he has no right to it."