Ali ibn al-Hasan ibn Faddal narrated from Muhammad ibn Isma'il, from Hammad ibn Isa, from Hariz, from Zurara:
Abu Ja'far عليه السلام said: "If a woman experiences menstruation while she is in a state of janabah (major ritual impurity), a single ghusl (ritual bath) suffices for both."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 1, p. 419