Musnad Ahmad 30:3132

Surayj narrated to us, he said: Fulayh narrated to us, from Muhammad ibn Abdullah ibn Husayn al-Aslami, from Ubaydullah ibn Sabihah, from Abu Hurayrah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "The best of charity is the *minihah* (loaning a milking animal). It goes out with a reward, and it returns with a reward. The *minihah* of a she-camel is like the freeing of a red slave, and the *minihah* of a ewe is like the freeing of a black slave."