What is the ruling on this situation in Islam?

If the husband divorced his other wife three times, she has become irrevocably separated from him (baynunah kubra), and she is not lawful for him until she marries another husband. The occurrence of the third divorce during menstruation does not prevent its validity according to the majority of scholars. This wife has become a stranger to her husband, and this is not contingent on him giving her a divorce certificate. She may marry after the expiration of her waiting period (iddah). It is not permissible for the husband to leave her in suspension or prevent her from marrying. It is forbidden for him to be alone with her (khalwah), and his visit to his daughters does not permit him to look at her except with complete hijab. Istikhara (prayer for guidance) is not legislated for such a matter and has no effect.