فَإِن طَلَّقَهَا فَلاَ تَحِلُّ لَهُ مِن بَعْدُ حَتَّىَ تَنكِحَ زَوْجًا غَيْرَهُ فَإِن طَلَّقَهَا فَلاَ جُنَاحَ عَلَيْهِمَا أَن يَتَرَاجَعَا إِن ظَنَّا أَن يُقِيمَا حُدُودَ اللّهِ وَتِلْكَ حُدُودُ اللّهِ يُبَيِّنُهَا لِقَوْمٍ يَعْلَمُونَ
[2:230]
So if he divorces her she shall not be lawful to him afterwards until she marries another husband; then if he divorces her there is no blame on them both if they return to each other (by marriage), if they think that they can keep within the limits of Allah, and these are the limits of Allah which He makes clear for a people who know.
So if a husband divorces his wife (irrevocably), He cannot, after that, re-marry her until after she has married another husband and He has divorced her. In that case there is no blame on either of them if they re-unite, provided they feel that they can keep the limits ordained by Allah. Such are the limits ordained by Allah, which He makes plain to those who understand.
And if he hath divorced her (the third time), then she is not lawful unto him thereafter until she hath wedded another husband. Then if he (the other husband) divorce her it is no sin for both of them that they come together again if they consider that they are able to observe the limits of Allah. These are the limits of Allah. He manifesteth them for people who have knowledge.