It is narrated from Sayyidah Aishah (may Allah be pleased with her) that Umm Habibah (may Allah be pleased with her) asked the Messenger of Allah (peace and blessings be upon him) about the blood. Sayyidah Aishah (may Allah be pleased with her) says: I saw her tub filled with blood. The Messenger of Allah (peace and blessings be upon him) said to her: "Wait for as long as your menstruation used to hold you back, then take a ritual bath." (b) Muslim recorded it in his Sahih from Qutaybah bin Sa'id. So in both narrations the Messenger of Allah (peace and blessings be upon him) placed her, once her menstruation had ended or as much time had passed as her menstruation used to hold her back, under the ruling of women who are pure, and he did not order her to wait extra days as a precaution (istizhar). Something suggesting that has been narrated in a weak hadith.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحيض / 1567