During 39 and 40 AH, Muawiyah ibn Abu Sufyan organized bands of murderers and brigands to enter border towns and to carry on loot, plunder, arson and rape. At that time Kumayl was the governor of Heet. Kumayl asked Imam Ali ibn Abi Talib's (as) permission to organize similar bands and carry plunder in the province of Circiea which was under the control of Muawiyah ibn Abu Sufyan. Imam Ali ibn Abi Talib (as) replied:
I never expected such a suggestion from a man like you. It is nobler and more moral to guard your people and province than to plunder others. They might be our enemies but they are also human beings. They consist of civil population comprising of' women and children how call one loot, plunder and kill them. No, never even dream of such a venture.
Source: islamicoccasions.com