Hakim bin Iqal says: I asked Sayyidah Aishah (may Allah be pleased with her): What is forbidden to me from my wife while I am fasting? She said: Her private part. I said: What is forbidden to me from my wife when she is menstruating? She said: Her private part.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحيض / 1509