Sahih Bukhari
Menstrual Periods
Volume: 001 / Book Number: 006 / Hadith Number: 329
Narrated Maimuna:
(the wife of the Prophet) During my menses, I never prayed, but used to sit on the mat beside the mosque of Allah's Apostle. He used to offer the prayer on his sheet and in prostration some of his clothes used to touch me."