Musannaf Ibn Abi Shayba 13:288

Waki’ narrated to us, from Hammad ibn Salamah, from Hakim al-Athram, from Abu Tamimah, from Abu Musa, that he addressed them and said: "I do not know of a man who bought a slave girl, then looked at what is below the slave girl [i.e., her private parts] and what is above the knee, except that I would punish him."