Proverbs 11:17 in the King James Version
The merciful man doeth good to his own soul: but he that is cruel troubleth his own flesh.
Context
16 A gracious woman obtains honor, but violent men obtain riches.
17 The merciful man does good to his own soul, but he who is cruel troubles his own flesh.
18 Wicked people earn deceitful wages, but one who sows righteousness reaps a sure reward.