Narrated Abdullah ibn Abbas:Divorced women shall wait concerning themselves for three monthly periods. Nor is it lawful for them to hide what Allah hath created in their wombs. This means that if a man divorced his wife he had the right to take her back in marriage though he had divorced her by three pronouncements. This was then repealed (by a Qur'anic verse). Divorce is only permissible twice.
حَدَّثَنَا أَحْمَدُ بْنُ مُحَمَّدٍ الْمَرْوَزِيُّ، حَدَّثَنِي عَلِيُّ بْنُ حُسَيْنِ بْنِ وَاقِدٍ، عَنْ أَبِيهِ، عَنْ يَزِيدَ النَّحْوِيِّ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، قَالَ { وَالْمُطَلَّقَاتُ يَتَرَبَّصْنَ بِأَنْفُسِهِنَّ ثَلاَثَةَ قُرُوءٍ وَلاَ يَحِلُّ لَهُنَّ أَنْ يَكْتُمْنَ مَا خَلَقَ اللَّهُ فِي أَرْحَامِهِنَّ } الآيَةَ وَذَلِكَ أَنَّ الرَّجُلَ كَانَ إِذَا طَلَّقَ امْرَأَتَهُ فَهُوَ أَحَقُّ بِرَجْعَتِهَا وَإِنْ طَلَّقَهَا ثَلاَثًا فَنُسِخَ ذَلِكَ وَقَالَ{ الطَّلاَقُ مَرَّتَانِ }.
AbuDaud
Divorce (Kitab Al-Talaq) • Hadith 2195