I have often wondered about the difference between mercy and grace as used in the Bible. In the past, I have tended to see them as almost synonymous and therefore interchangeable.
After further consideration, I now conclude that there is a significant difference between these two terms. Mercy derives from law. Grace is a product of love. Mercy reflects Moses and OT thinking. Grace reflects Jesus and the conclusion of the biblical story.
Mercy says I erred and deserve punishment, but that forgiveness will allow me to escape. Mercy leaves me with a sense of guilt and unworthiness, despite my escape from what is rightfully due. Mercy is only enjoyed because higher authority stoops to grant an unmerited favor to an undeserving lesser being.
Grace on the other hand says there never was any offense. Grace refuses to recognize any guilt or need for forgiveness. Grace is exactly what we all freely give to those we truly love, like our own children. Their malfeasance and frailties are never grounds for rejection because love is blind to faults and failings. There is no condescension in grace, only the assurance of inherent worthiness and unfailing regard. Grace, like love, never fails.