Sahih Bukhari Volume 3, Book 33, Hadith 2038

حَدَّثَنَا قُتَيْبَةُ، حَدَّثَنَا يَزِيدُ بْنُ زُرَيْعٍ، عَنْ خَالِدٍ، عَنْ عِكْرِمَةَ، عَنْ عَائِشَةَ ـ رضى الله عنها ـ قَالَتِ اعْتَكَفَتْ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم امْرَأَةٌ مِنْ أَزْوَاجِهِ مُسْتَحَاضَةٌ، فَكَانَتْ تَرَى الْحُمْرَةَ وَالصُّفْرَةَ، فَرُبَّمَا وَضَعْنَا الطَّسْتَ تَحْتَهَا وَهْىَ تُصَلِّي‏.‏

Narrated By 'Aisha : One of the wives of Allah's Apostle practiced Itikaf with him while she ad bleeding in between her periods and she would see red (blood) or yellowish traces, and sometimes we put a tray beneath her when she offered the prayer.