It was narrated from Ibn 'Umar that the Prophet (ﷺ) said, concerning a man who had a wife and he divorced her, then she married another man who divorced her before consummating the marriage with her, and (it was asked) whether she could go back to her first husband: "No, not until she tastes his sweetness."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ عَلْقَمَةَ بْنِ مَرْثَدٍ، قَالَ سَمِعْتُ سَالِمَ بْنَ رَزِينٍ، يُحَدِّثُ عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم فِي الرَّجُلِ تَكُونُ لَهُ الْمَرْأَةُ يُطَلِّقُهَا ثُمَّ يَتَزَوَّجُهَا رَجُلٌ آخَرُ فَيُطَلِّقُهَا قَبْلَ أَنْ يَدْخُلَ بِهَا فَتَرْجِعَ إِلَى زَوْجِهَا الأَوَّلِ قَالَ " لاَ حَتَّى تَذُوقَ الْعُسَيْلَةَ " .
sunnah.com