It was narrated from 'Aishah that a man divorced his wife three times and she married another husband who divorced her, before having intercourse with her. The Messenger of Allah was asked:"Is she permissible for the first (husband to remarry her)?" He said: "No, not until he tastes her sweetness as the first tasted her sweetness."
أَخْبَرَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، قَالَ حَدَّثَنَا يَحْيَى، قَالَ حَدَّثَنِي عُبَيْدُ اللَّهِ، قَالَ حَدَّثَنِي الْقَاسِمُ، عَنْ عَائِشَةَ، أَنَّ رَجُلاً، طَلَّقَ امْرَأَتَهُ ثَلاَثًا فَتَزَوَّجَتْ زَوْجًا فَطَلَّقَهَا قَبْلَ أَنْ يَمَسَّهَا فَسُئِلَ رَسُولُ اللَّهِ صلى الله عليه وسلم أَتَحِلُّ لِلأَوَّلِ فَقَالَ " لاَ حَتَّى يَذُوقَ عُسَيْلَتَهَا كَمَا ذَاقَ الأَوَّلُ " .
Nesai
The Book of Divorce • Hadith 3412