Musannaf Ibn Abi Shaybah

Hazrat Yahya bin Saeed says that I sent a messenger to the mother of Ra'itah. He came and informed me that Umm 'Amrah used to say to women that when any of you inserts cotton wool in her private part and finds its color changed (i.e., stained), she should not pray until she sees something (i.e., blood) (i.e., blood).