Musannaf Ibn Abi Shayba 1:993

Abu Bakr narrated to us, he said: Abu Bakr ibn Ayyash narrated to us, from Abu Ishaq, from al-Harith, from Ali, who said: She shall sprinkle her private part with water and perform wudu. If it is thick blood upon her, she shall perform ghusl and use a stuffing (tampon/pad), for it is only a strike from the devil. If she does that once or twice, it will go away.