(a) Hisham narrated from his father that Fatimah bint Abi Hubaysh (may Allah be pleased with her) said: O Messenger of Allah, I have istihadah and do not become pure, and he mentioned the hadith. In it, he (peace and blessings be upon him) said: "Perform ghusl at the time of your purity and perform ablution for prayer."
In one narration: "Perform ablution for every prayer." (b) The Shaykh said: The correct view is that this is the saying of Urwah bin al-Zubayr (may Allah have mercy on him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحيض / 1623