Sayyidah Maymunah (may Allah be pleased with her), the wife of the Prophet (peace and blessings be upon him), said: "The Messenger of Allah (peace and blessings be upon him) used to touch any of his wives while she was menstruating, if she had on a waist-wrapper reaching the middle of her thighs or her knees."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20390