The Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, narrated to me from Abu Al-Qasim Ja’far ibn Muhammad, from Muhammad ibn Ya’qub, from Ali ibn Ibrahim, from his father, in a marfu’ narration: A woman asked Abu Abdullah عليه السلام, saying: "I used to refrain from prayer during my nifas (postnatal bleeding) for twenty days until I was advised to reduce it to eighteen days." Abu Abdullah عليه السلام replied: "And why were you advised to reduce it to eighteen days?" A man interjected: "Because of the narration reported from the Messenger of Allah سبحانه وتعالى (peace be upon him and his family), where he told Asma bint Umays, after she had given birth to Muhammad ibn Abi Bakr, to follow this ruling." Abu Abdullah عليه السلام said: "Asma bint Umays asked the Messenger of Allah سبحانه وتعالى (peace be upon him and his family) about her situation after eighteen days. Had she asked him before that, he would have instructed her to perform ghusl earlier and to act as a mustahadah (a woman experiencing irregular bleeding)."