Sunan An-Nasai, Chapter: The Book of Purification

that Umm Habibah bint Jahsh who was married to Abdur-Rahman bin Awf suffered from Istihadah (non-menstrual vaginal bleeding) and did not become pure. Her situation was mentioned to the Messenger of Allah (saw) and he said: 'That is not menstruation, rather it is a kick* in the womb, so let her work out the length of the menses that she used to have, and stop praying (for that period of time), then after that let her perform Ghusl for every prayer.'" (Sahih) *A kick in the womb: in other narrations means "A kick from Shaitan,", meaning that the Shaitan uses it to confuse her about her religious commitment.