Musnad Ahmad 1153:1962

Yazid narrated to us, Hajjaj informed us, from Abd al-Rahman ibn al-Aswad, from his father, from Aisha, who said: When the Messenger of Allah (peace and blessings of Allah be upon him) wanted to have intimate contact with one of us while she was menstruating, he would order her, and she would wrap an izar (a garment covering the lower part of the body). And when he wanted to sleep while he was in a state of janabah (major ritual impurity), he would perform wudu, like his wudu for prayer.