When the last pronouncement is made, the talak becomes final and irrevocable. It is necessary that each of the three pronouncements should be made at a time when no intercourse has taken place during that period of tuhr. For instance, W, a wife, is having her period of purity and no sexual intercourse has taken place. At this time, her husband, H, pronounces talak on her. This is first pronouncement. Thereafter, H resumes sexual intercourse with W, or revokes the pronouncement by express words. Then, again, when the wife gets the next period of purity, and before he indulges in sexual intercourse, H makes a pronouncement of divorce on her.
This is second pronouncement. H again revokes it. Again, when the wife enters her third period of purity and before any intercourse takes place, H makes a pronouncement of divorce.
This is third pronouncement. The moment H utters the third pronouncement, the marriage stands dissolved irrevocably, irrespective of idda. The significance of the hasan form of talak can be understood only in the background of the pre-Islamic Arabian practice, under which pronouncement of divorce in one tuhr, followed by its revocation, and again a pronouncement followed by revocation could go on endlessly, leading to misery, harassment and humiliation of women. To put an end to this vicious practice, the Prophet laid down that the divorce will become final and irrevocable at the third pronouncement. To impose a further deterrent on this arbitrary practice, it was laid down that the parties were not free to remarry unless the wife married another man who had actually consummated the marriage, and then divorced her. On the completion of idda, the woman could marry her former husband.
This is a penal provision meant to chastise the husband who repudiates his wife thoughtlessly. No thoughts were wasted on the fact that it was a greater punishment and humiliation to the woman.