Sayyidah Umm Ayman (may Allah be pleased with her) said: I heard the Messenger of Allah (peace and blessings be upon him) saying: "The 'black' one (that is, the lowly one) is only the one who is so because of his belly and his private parts."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21691