Language:
كتاب الحيض
6  
Menstrual Periods
(10)
Chapter: The I'tikaf of a woman who is bleeding in between her periods
(10)
باب الاِعْتِكَافِ لِلْمُسْتَحَاضَةِ
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.‏
Reference : Sahih al-Bukhari 311
In-book reference : Book 6, Hadith 16
USC-MSA web (English) reference : Vol. 1, Book 6, Hadith 308
  (deprecated numbering scheme)