It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "A woman in postnatal bleeding should wait forty nights. If she becomes pure before that, she is pure; and if she exceeds forty days, she is in the position of a woman with istihadah: she should take a ritual bath and pray, and if the blood overwhelms her, she should perform ablution for every prayer." Amr bin al-Husayn and Muhammad bin Ulathah do not meet the condition of the two Shaykhs, but I have mentioned it as a supporting report.