The Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, narrated to me from Ahmad ibn Muhammad, from his father, from Muhammad ibn Yahya, and Al-Husayn ibn Ubayd Allah سبحانه وتعالى, from Ahmad ibn Muhammad ibn Yahya, from his father Muhammad ibn Yahya, from Muhammad ibn Ali ibn Mahbub, from Muhammad ibn Isa Al-Ubaydi, from Al-Husayn ibn Sa'id, from Al-Nadr, from Abu Sa'id, from Abu Basir, from Abu Abdullah and Abu Ja'far عليه السلام. They said: Imam عليه السلام said: "Prayer does not need to be repeated because of blood that one did not notice, except for menstrual blood. For menstrual blood, whether small or large, whether it was seen or unseen on the clothing, it is the same and must be removed."