What is the ruling on sexual intercourse that occurred between a couple on the last day of the three months following a verbal and formal divorce, believing it to be the waiting period (iddah)? Is this intercourse considered zina (fornication/adultery)? What are the legal consequences of this according to Islamic law? Is the wife required to observe a waiting period after the husband pronounced the oath of divorce to her over the phone? And what is the duration of this waiting period?

The waiting period (iddah) for a divorced woman ends after three menstrual cycles for those who menstruate, by delivering the baby for a pregnant woman, and after three months for a young girl or an elderly woman who has despaired of menstruation. If the husband divorced his wife with less than three pronouncements, and had intercourse with her before the end of her waiting period of three menstrual cycles, then his intercourse is permissible, and she returns to his marital bond according to some scholars. However, if he had intercourse with her after the waiting period has ended, then the intercourse is forbidden and considered zina (adultery) if they both knew of its prohibition. Repentance is obligatory, and this act does not result in a return to the marriage. No new divorce can affect her after the waiting period except through a new marriage contract.