What is the ruling of Islamic law regarding a wife returning to the second husband she married with the intention of making herself lawful for her first husband, then she changed her intention and desired to stay with him? Does this marriage count as a tahlīl marriage if she returns to him, and what is the ruling concerning the first husband if she marries him after this repentance?

If a man divorces his wife for the third time, she is not lawful for him until she marries another husband in a marriage of desire, not a marriage of analysis (tahleel), and then he dies or divorces her. This is based on the Almighty's saying: (And if he has divorced her [for the third time], then she is not lawful to him afterward until she marries another husband) and the Prophet's (peace be upon him) saying: "No, until you taste his sweetness and he tastes your sweetness."

As for a marriage of analysis (tahleel), which is when a man marries her with the intention of making her lawful for her first husband, it is forbidden and invalid according to Sharia. The woman does not become lawful for her first husband through it, whether the intention is declared or merely intended. The one who does so is cursed, as the Prophet (peace be upon him) said: "Allah has cursed the one who makes a woman lawful [for her former husband] and the one for whom she is made lawful."

This invalid marriage is as if it never existed. If the second husband divorces her, he does not have the right to take her back. The solution is a valid marriage contract with the intention of desire, not analysis. If he dies or divorces her after this valid marriage, she becomes lawful for the first husband.