Yazid bin Babanus said: I said to Sayyidah Aishah (may Allah be pleased with her): What do you say about al-'irak? She said: "Do you mean menstruation?" We said: Yes. She said: "Call it by the name that Allah has given it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1473