Musannaf Ibn Abi Shaybah 40718 — Reports on the Khawarij

Mughirah said: Umar bin Abd al-Aziz debated with the Khawarij, and those of them who were to return returned. One band of them refused to return. Umar bin Abd al-Aziz sent an army of horsemen towards them and ordered them to go to wherever the Khawarij stopped, and not to interfere with them or provoke them. If they killed and spread corruption in the land, they were to attack them and fight them; and if they did not kill and did not spread corruption in the land, they were to leave them and let them go on their way.