Musnad Abu Ya'la al-Mawsili 142:5

Abu Hammam narrated to us, Abd al-A’la narrated to us, Jald ibn Ayyub narrated to us, from Mu’awiyah ibn Qurrah, from Anas ibn Malik, who said: "The menstruating woman shall wait five, seven, eight, nine, or ten [days]. If the ten [days] have passed, then she is a *mustahada* (a woman experiencing irregular vaginal bleeding)."