And if he has divorced her [for the third time], then she (2:230)

﴿فَإِن طَلَّقَهَا فَلَا تَحِلُّ لَهُ مِن بَعْدُ حَتَّىٰ تَنكِحَ زَوْجًا غَيْرَهُ ۗ فَإِن طَلَّقَهَا فَلَا جُنَاحَ عَلَيْهِمَا أَن يَتَرَاجَعَا إِن ظَنَّا أَن يُقِيمَا حُدُودَ اللَّهِ ۗ وَتِلْكَ حُدُودُ اللَّهِ يُبَيِّنُهَا لِقَوْمٍ يَعْلَمُونَ﴾
[ البقرة: 230]

2:230 And if he has divorced her [for the third time], then she is not lawful to him afterward until [after] she marries a husband other than him. And if the latter husband divorces her [or dies], there is no blame upon the woman and her former husband for returning to each other if they think that they can keep [within] the limits of Allah. These are the limits of Allah, which He makes clear to a people who know.

If the husband divorces her for the third time, he may not remarry her until she gets married to another man in a valid marriage that is genuine and not merely contracted to make her lawful for the original husband, and where sexual intercourse has taken place in this later marriage.
Should the second husband divorce her or pass away, the woman and her first husband may return to one another with a new marriage contract and dowry, if they feel that they will fulfil the rights of each other set-out in the sacred law.
These rules are made clear by Allah for people who know His laws and limits, as they are the ones who benefit from them.

And if he has divorced her (the third time), then she is not lawful unto him thereafter until she has married another husband. Then, if the other husband divorces her, it is no sin on both of them that they reunite, provided they feel that they can keep the limits ordained by Allah. These are the limits of Allah, which He makes plain for the people who have knowledge.

phonetic Transliteration

Fain tallaqaha fala tahillu lahu min baAAdu hatta tankiha zawjan ghayrahu fain tallaqaha fala junaha AAalayhima an yatarajaAAa in thanna an yuqeema hudooda Allahi watilka hudoodu Allahi yubayyinuha liqawmin yaAAlamoona

Abdullah Yusuf Ali - Translation

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.

Safi-ur-Rahman al-Mubarakpuri

And if he has divorced her (the third time), then she is not lawful unto him thereafter until she has married another husband. Then, if the other husband divorces her, it is no sin on both of them that they reunite, provided they feel that they can keep the limits ordained by Allah. These are the limits of Allah, which He makes plain for the people who have knowledge.

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