Sura al-Baqara 2:230

فَإِن طَلَّقَهَا فَلَا تَحِلُّ لَهُۥ مِنۢ بَعْدُ حَتَّىٰ تَنكِحَ زَوْجًا غَيْرَهُۥ فَإِن طَلَّقَهَا فَلَا جُنَاحَ عَلَيْهِمَآ أَن يَتَرَاجَعَآ إِن ظَنَّآ أَن يُقِيمَا حُدُودَ ٱللَّـهِ وَتِلْكَ حُدُودُ ٱللَّـهِ يُبَيِّنُهَا لِقَوْمٍ يَعْلَمُونَ

fa-in ṭallaqahā fa-lā taḥillu lahu min baʿdu ḥattā tankiḥa zawjan ghayrahu fa-in ṭallaqahā fa-lā junāḥa ʿalayhimā an yatarājaʿā in ẓannā an yuqīmā ḥudūda allāhi wa-tilka ḥudūdu allāhi yubayyinuhā li-qawmin yaʿlamūna

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.

Sura al-Baqara 2:232

وَإِذَا طَلَّقْتُمُ ٱلنِّسَآءَ فَبَلَغْنَ أَجَلَهُنَّ فَلَا تَعْضُلُوهُنَّ أَن يَنكِحْنَ أَزْوَٰجَهُنَّ إِذَا تَرَٰضَوْا۟ بَيْنَهُم بِٱلْمَعْرُوفِ ذَٰلِكَ يُوعَظُ بِهِۦ مَن كَانَ مِنكُمْ يُؤْمِنُ بِٱللَّـهِ وَٱلْيَوْمِ ٱلْأَخِرِ ذَٰلِكُمْ أَزْكَىٰ لَكُمْ وَأَطْهَرُ وَٱللَّـهُ يَعْلَمُ وَأَنتُمْ لَا تَعْلَمُونَ

wa-idhā ṭallaqtumu l-nisāʾa fa-balaghna ajalahunna fa-lā taʿḍulūhunna an yankiḥna azwājahunna idhā tarāḍaw baynahum bil-maʿrūfi dhālika yūʿaẓu bihi man kāna minkum yuʾminū billāhi wa-l-yawmi l-akhiri dhālikum azka la-kum wa-aṭharu wallāhu yaʿlamu wa-antum lā taʿlamūna

When ye divorce women, and they fulfil the term of their ('Iddat), do not prevent them from marrying their (former) husbands, if they mutually agree on equitable terms. This instruction is for all amongst you, who believe in Allah and the Last Day. That is (the course Making for) most virtue and purity amongst you and Allah knows, and ye know not.