Majma al-Zawaid 7246 — Freeing red and black slaves

Sayyiduna Abu Hurayrah (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "The best charity is that given as a lent gift, which brings reward in the morning and brings reward in the evening: giving a she-camel as such a gift, which is like freeing a red-skinned (that is, fair-skinned) slave, and giving a goat as such a gift, which is like freeing a black-skinned slave."
Ahmad recorded it; its chain contains a narrator, Ubaydullah bin Subayhah, whom I do not know; the rest of its narrators are thiqat (trustworthy).