It was narrated that 'Aishah said:
"The Messenger of Allah said to me: 'Get me a mat from the mosque.' I said: 'I am menstruating.' He said: 'Your menstruation is not in your hand.'" (DE)
English reference (DE): Vol. 1, Book 1, Hadith 632 (DE)
Arabic reference (DE): Book 1, Hadith 675 (DE)