Imam Baqir (peace be upon him): Any divorce that is not according to the Sunnah, or any divorce that is not according to the ʿiddah (the prescribed waiting period), has no value. Zurarah said: I asked Imam Baqir (peace be upon him): "Explain to me the divorce of the Sunnah and the divorce of the ʿiddah." He said: "As for the divorce of the Sunnah, whenever a man wishes to divorce his wife, he must wait until she menstruates and then becomes pure. So when she has passed her menstrual period, he should divorce her once without having had intercourse with her, and bring two witnesses to this. Then he leaves her until she menstruates twice more, so her ʿiddah is completed with three menstruations, and at that point she is separated from him, and that man becomes one of her suitors — if he wishes he may marry her, and if he wishes he may not. As long as she is in her ʿiddah, her maintenance and lodging are the man's responsibility, and until the end of the ʿiddah they inherit from one another." He said: "As for the divorce of the ʿiddah, concerning which Allah the Exalted says: فَطَلِّقُوهُنَّ لِعِدَّتِهِنَّ وَ أَحْصُوا الْعِدَّةَ [divorce them for their prescribed time, and calculate the number of the days prescribed], [it must be said]: if a man among you wishes to divorce his wife with the divorce of the ʿiddah, he must wait until she menstruates and comes out of her menstruation, then divorce her once without having had intercourse with her, and bring two just witnesses. If he wishes, he may take her back on that same day or a few days after, before she menstruates. He must bring witnesses to his taking her back, and have intercourse with her, and remain with her until she menstruates. Then if she menstruates and comes out of her menstruation, he divorces her once again without having had intercourse with her, and brings witnesses to that. Then he may again, whenever he wishes, take her back before she menstruates, bring witnesses to his taking her back, have intercourse with her, and she remains with him until she menstruates for the third time. When she comes out of her third menstruation, he divorces her for the third time without having had intercourse with her, and brings witnesses to that. When he has done that, she is separated from him, and it is not lawful for him to marry her unless she marries another husband." It was said to him: "What if she is among those who do not menstruate?" He said: "Such a woman is divorced by the divorce of the Sunnah."