Narrated by the Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, from Abu al-Qasim Ja'far ibn Muhammad, from Muhammad ibn Ya'qub, from Ali ibn Ibrahim, from his father, from Ibn Abi Umayr, from Hafs ibn al-Bukhtari, who said: A woman entered upon Abu Abdullah عليه السلام and asked Imam عليه السلام about a woman who experiences continuous blood flow and does not know whether it is menstruation or something else. Imam عليه السلام said to her: "The blood of menstruation is hot, thick, and black with force and warmth. The blood of istihadha is yellow and cold. If the blood has warmth, force, and blackness, then she should refrain from prayer." He (Narrator) said: She left, saying, "If he were a woman, he could not have explained it better than this." (aghast by the knowledge of the Imam عليه السلام)