It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him); he said that the Messenger of Allah (peace and blessings be upon him) said: "A borrowed item ('ariyah) is to be returned, a manihah (an animal given for its milk) is to be returned, and whoever finds a she-camel whose udder has been tied (to deceptively show more milk), it is not lawful for him to keep its tying (for his own benefit) until he returns it."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7606