Musannaf Ibn Abi Shaybah 1378 — What a woman with irregular bleeding

Anas bin Sirin said: "A woman from the family of Anas developed istihadah, and they told me to find out (the ruling). I asked Sayyiduna Ibn Abbas (may Allah be pleased with them both), and he said: 'As long as she sees the dark red (menstrual) blood, she should not pray; and if she sees purity even for a part of the day, she should take a ritual bath and pray.'"