Musnad Ahmad 1311:2

Yahya ibn Abi Bukayr narrated to us, he said: Isra’il narrated to us, from Uthman ibn Sa’d, from Abdullah ibn Abi Mulaykah, he said: My maternal aunt, Fatimah bint Abi Hubaysh, narrated to me, she said: I came to Aisha and said to her: "O Mother of the Believers, I fear that I have no share in Islam, and that I am among the people of the Fire. I remain for as long as Allah wills from the day I experience *istihada* (prolonged vaginal bleeding), and I do not perform a prayer for Allah, the Mighty and Majestic." She said: "Sit until the Prophet, peace and blessings of Allah be upon him, comes." When the Prophet, peace and blessings of Allah be upon him, came, she said: "O Messenger of Allah, this is Fatimah bint Abi Hubaysh; she fears that she has no share in Islam, and that she is among the people of the Fire. She remains for as long as Allah wills from the day she experiences *istihada*, and she does not perform a prayer for Allah, the Mighty and Majestic, during it." He said: "Command Fatimah bint Abi Hubaysh to count every month the number of days of her menstrual cycle, then perform ghusl, insert a cotton pad (to absorb the blood), bind herself with a cloth, clean herself, then purify herself for every prayer, and pray. For that is only a kick from the devil, or a vein that has ruptured, or an ailment that has afflicted her."