Ahmad ibn Muhammad, from Al-Barqi, from Isma'il, from Umar ibn Hanzala:
I said to Abu Abdullah عليه السلام: "What is permissible for a man with his menstruating wife?" Imam عليه السلام said: "Whatever is between the thighs."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 1, p. 162