Grace is the unmerited, undeserved favor that God extends towards us. Mercy is the compassion or forgiveness shown toward someone whom it is within one's power to punish or harm. In a nutshell, grace gives us what we don't deserve; mercy does not give us what we do deserve!
We don't deserve favor, but we do deserve death. God extended both to us as sinners and because He extended both unto us, our godly sorrow should work repentance. I receive both of them from God and in exchange, I give Him my obedience. That is a fair exchange and the least we can do. Obedience is our reasonable service!
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