Sahih al-Bukhari 311
Narrated `Aisha:
One of the mothers of the faithful believers (i.e. the wives of the Prophet (ﷺ) ) did I`tikaf while she was 
having bleeding in between her periods.
حَدَّثَنَا مُسَدَّدٌ، قَالَ حَدَّثَنَا مُعْتَمِرٌ، عَنْ خَالِدٍ، عَنْ عِكْرِمَةَ، عَنْ عَائِشَةَ، أَنَّ بَعْضَ، أُمَّهَاتِ الْمُؤْمِنِينَ اعْتَكَفَتْ وَهْىَ مُسْتَحَاضَةٌ‏.‏