Sahih al-Bukhari 7160
Narrated `Abdullah bin `Umar:
That he had divorced his wife during her menses. `Umar mentioned that to the Prophet. Allah's 
Apostle became angry and said, "He must take her back (his wife) and keep her with him till she 
becomes clean from her menses and then to wait till she gets her next period and becomes clean again 
from it and only then, if he wants to divorce her, he may do so."
حَدَّثَنَا مُحَمَّدُ بْنُ أَبِي يَعْقُوبَ الْكِرْمَانِيُّ، حَدَّثَنَا حَسَّانُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا يُونُسُ، قَالَ مُحَمَّدٌ أَخْبَرَنِي سَالِمٌ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، أَخْبَرَهُ أَنَّهُ، طَلَّقَ امْرَأَتَهُ وَهْىَ حَائِضٌ، فَذَكَرَ عُمَرُ لِلنَّبِيِّ صلى الله عليه وسلم، فَتَغَيَّظَ فِيهِ رَسُولُ اللَّهِ صلى الله عليه وسلم ثُمَّ قَالَ ‏
"‏ لِيُرَاجِعْهَا، ثُمَّ لْيُمْسِكْهَا حَتَّى تَطْهُرَ، ثُمَّ تَحِيضَ فَتَطْهُرَ، فَإِنْ بَدَا لَهُ أَنْ يُطَلِّقَهَا فَلْيُطَلِّقْهَا ‏"‏‏.‏