Sayyidah Maymunah (may Allah be pleased with her) said: "Whenever the Messenger of Allah (peace and blessings be upon him) wanted to touch one of his wives while she was menstruating, he would order her to wear a waist-wrapper, then he would touch her."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20379