The Prophet ﷺ said, "When the menstrual period begins, leave off the prayer, and when it ends, perform the ritual bath."
أخبرنا هشام بن عمار قال حدثنا سهل بن هاشم قال حدثنا الأوزاعي عن الزهري عن عروة
أن النبي ﷺ قال إذا أقبلت الحيضة فاتركي الصلاة وإذا أدبرت فاغتسلي
Sahih. Ibn Majah reported it in the Book of Purification, chapter on what has been said about the woman with prolonged bleeding when her condition becomes confused... etc, hadith 626, from the hadith of Uzai with this wording, and it is in Al-Kubra, hadith 210, see also the previous hadith. Bukhari also reported it in the Book of Menstruation, chapter 26, hadith 327, and Muslim in the Book of Menstruation, chapter 14, hadith 334, from the hadith of Zuhri with this wording, see also the coming hadith.