Musannaf Ibn Abi Shayba 3:1940

Muhammad ibn Bakr narrated to us, from Ibn Jurayj, from ‘Ata’, who said: I said to him, "What do you think if a menstruating woman passes by a group of people who are reciting the Mushaf (Quran), and they prostrate—should she prostrate with them?" He said, "No, she has already been prevented from something better than that."