Sunan an Nasai
The Book of Menstruation and Istihadah
Hadith #4
3.4
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنِ ابْنِ شِهَابٍ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، قَالَتِ اسْتَفْتَتْ أُمُّ حَبِيبَةَ بِنْتُ جَحْشٍ رَسُولَ اللَّهِ صلى الله عليه وسلم فَقَالَتْ يَا رَسُولَ اللَّهِ إِنِّي أُسْتَحَاضُ فَقَالَ " إِنَّ ذَلِكِ عِرْقٌ فَاغْتَسِلِي ثُمَّ صَلِّي " . فَكَانَتْ تَغْتَسِلُ عِنْدَ كُلِّ صَلاَةٍ .
It was narrated that 'Aishah said:"Umm Habibah bint Jahsh asked the Messenger of Allah (ﷺ): 'O Messenger of Allah, I suffer from Istihadah.' He said: 'That is a vein, so perform Ghusl, then pray.' And she used to perform Ghusl for each prayer