(27) The Book of Divorce
كتاب الطلاق
(4) Chapter: Divorce Without The 'Iddah
(4) باب الطَّلاَقِ لِغَيْرِ الْعِدَّةِ ‏‏
Sunan an-Nasa'i 3398 
It was narrated from Ibn 'Umar that he divorced his wife when she was menstruating, but the Messenger of Allah told him to take her back, and divorce her when she was pure (not menstruating).
أَخْبَرَنِي زِيَادُ بْنُ أَيُّوبَ، قَالَ حَدَّثَنَا هُشَيْمٌ، قَالَ أَخْبَرَنَا أَبُو بِشْرٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عُمَرَ، أَنَّهُ طَلَّقَ امْرَأَتَهُ وَهِيَ حَائِضٌ فَرَدَّهَا عَلَيْهِ رَسُولُ اللَّهِ صلى الله عليه وسلم حَتَّى طَلَّقَهَا وَهِيَ طَاهِرٌ ‏.‏
Grade :  Sahih (Darussalam)
Reference : Sunan an-Nasa'i 3398
In-book reference : Book 27, Hadith 10
English translation : Vol. 4, Book 27, Hadith 3427