Sunan an Nasai 3558
The Book of Divorce
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 .
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
Grading: Abu Ghuddah: Sahih · Al-Albani: Sahih · Zubair Ali Zai: Isnaad Sahih
Text from the public-domain hadith-api dataset. Numbering follows that dataset and can differ by a few from some printed editions — check the wording, not only the number.