Amir al-Sha'bi (may Allah have mercy on him) reported that the Messenger of Allah (peace and blessings be upon him) said: "Whoever finds an animal whose owners had become unable to feed it, so they let it go, and then someone takes it and revives it (restores it to health), it belongs to him (the one who cared for it)." Ubaydullah said: I asked: From whom is this hadith reported? He (al-Sha'bi) said: It is reported from several of the noble Companions (may Allah be pleased with them).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللقطة / 12113