Is it permissible for a husband to take back his wife after divorcing her for the second time, especially after she has completed three menstrual cycles, and before the lapse of three full months from the date of the divorce?

A menstruating woman's waiting period (iddah) is calculated by menstrual cycles, not by months. So, if three menstrual cycles have passed after the divorce, her waiting period has ended, and she is irrevocably divorced from her husband with a minor separation. He cannot take her back except with a new contract. It is not permissible for a husband to abandon his wife and leave her suspended, nor to be absent from her for more than six months except with her consent.