Sunan an-Nasa'i, Hadith 3558 ⓘ
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 .
also referenced under: Book 27, Hadith 172 (In-Book) & Volume 4, Book 27, Hadith 3588 (DarusSalam)