Sunan an-Nasa'i 209
It was narrated from 'Aishah that Umm Habibah bint Jahsh who was married to 'Abdur-Rahman bin 'Awf suffered from Istihadah (non-mentrual vaginal bleeding) and did not become pure. Her situation was mentioned to the Messenger of Allah (ﷺ) and he said:
'That is not menstruation, rather it is a kick [1] 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 tie), then after that period of time), then after that let her perform Ghusl for every prayer.'"

[1] 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.
أَخْبَرَنَا الرَّبِيعُ بْنُ سُلَيْمَانَ بْنِ دَاوُدَ بْنِ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا إِسْحَاقُ بْنُ بَكْرٍ، قَالَ حَدَّثَنِي أَبِي، عَنْ يَزِيدَ بْنِ عَبْدِ اللَّهِ، عَنْ أَبِي بَكْرِ بْنِ مُحَمَّدٍ، عَنْ عَمْرَةَ، عَنْ عَائِشَةَ، أَنَّ أُمَّ حَبِيبَةَ بِنْتَ جَحْشٍ الَّتِي، كَانَتْ تَحْتَ عَبْدِ الرَّحْمَنِ بْنِ عَوْفٍ وَأَنَّهَا اسْتُحِيضَتْ لاَ تَطْهُرْ فَذُكِرَ شَأْنُهَا لِرَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَ ‏
"‏ إِنَّهَا لَيْسَتْ بِالْحَيْضَةِ وَلَكِنَّهَا رَكْضَةٌ مِنَ الرَّحِمِ فَلْتَنْظُرْ قَدْرَ قُرْئِهَا الَّتِي كَانَتْ تَحِيضُ لَهَا فَلْتَتْرُكِ الصَّلاَةَ ثُمَّ تَنْظُرْ مَا بَعْدَ ذَلِكَ فَلْتَغْتَسِلْ عِنْدَ كُلِّ صَلاَةٍ ‏"‏ ‏.‏