after a divorce for the third time it is not lawful for the husband to resume marital relations with her or remarry her until she has been married and divorced by another husband. in that case there is no sin for the former husband to marry her if they think that they can abide by the law. these are the laws of god. he explains them for the people of knowledge.
فإن طلقها فلا تحل له من بعد حتى تنكح زوجا غيره فإن طلقها فلا جناح عليهما أن يتراجعا إن ظنا أن يقيما حدود الله وتلك حدود الله يبينها لقوم يعلمون