It was narrated from Ibn 'Umar that he divorced his wife when she was menstruating, and the Messenger of Allah told him to take her back.

أَخْبَرَنَا يُوسُفُ بْنُ عِيسَى، - مَرْوَزِيٌّ - قَالَ حَدَّثَنَا الْفَضْلُ بْنُ مُوسَى، قَالَ حَدَّثَنَا حَنْظَلَةُ، عَنْ سَالِمٍ، عَنِ ابْنِ عُمَرَ، أَنَّهُ طَلَّقَ امْرَأَتَهُ وَهِيَ حَائِضٌ فَأَمَرَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم فَرَاجَعَهَا ‏.‏