Musannaf Ibn Abi Shayba 1:1562

Yazid ibn Harun narrated to us, from Hammad ibn Salamah, from Abd al-Rahman, from his paternal aunt, from Abu Rafi, that the Messenger of Allah (peace and blessings of Allah be upon him) went around to his wives in one night, and he performed ghusl (a ritual bath) at each one of them. I said, "O Messenger of Allah, would it not have been better if you had performed one ghusl?" He said, "This is purer and better," or "purer and cleaner."