Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 272
Narated By One of the Wives of the Prophet : Ikrimah reported on the authority of one of the wives of the Prophet (pbuh) saying: When the Prophet (pbuh) wanted to do something (i.e. kissing, embracing) with (his) menstruating wife, he would put a garment on her private part.