Hadithcore
Sahih al-Bukhari, 5253
sahih

Narrated Ibn `Umar:

(Divorcing my wife during her menses) was counted as one legal divorce.

وَقَالَ أَبُو مَعْمَرٍ حَدَّثَنَا عَبْدُ الْوَارِثِ، حَدَّثَنَا أَيُّوبُ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عُمَرَ، قَالَ حُسِبَتْ عَلَىَّ بِتَطْلِيقَةٍ‏.‏

References2 variants
In-Book Reference
Book 68, Hadith 3
USC-MSA web (English) reference
Vol. 7, Book 63, Hadith 180 (deprecated numbering scheme)