Fatimah bint Abu Hubaysh told me that she instructed Asma, or Asma told me that Fatimah bint Abu Hubaysh instructed her, to ask the Messenger of Allah ﷺ. He instructed her to refrain from prayer for the days she would normally refrain, then perform the ritual bath.
حدثنا يوسف بن موسى حدثنا جرير عن سهيل يعني ابن أبي صالح عن الزهري
حدثتني فاطمة بنت أبي حبيش أنها أمرت أسماء أو أسماء حدثتني أنها أمرتها فاطمة بنت أبي حبيش أن تسأل رسول الله ﷺ فأمرها أن تقعد الأيام التي كانت تقعد ثم تغتسل
Reference, [Its isnad is daif] Bayhaqi related it, 1/331, from the hadith of Abu Dawud through him. See also nos. 286, 296, and 304. Hisham bin Urwa narrated it from his father, as recorded by Nasai, 1/116. Zuhri is known to conceal the true nature of his transmission and narrated using the ambiguous form "an," though the hadith of Nasai is sahih, no. 1.