When demanding fair pay for hard work, we often say that a person should get what they deserve. Oddly, we use those same words when it comes time to sentence a convicted criminal. It is only fair when we get what we deserve. We call that justice. When you get better than you deserve, it is not justice at all. Instead, it's what we call mercy. God is not fair. God is merciful.
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A billboard for a hospital with the word "mercy" in its name once encouraged drivers-by to go to that hospital with the words "you deserve mercy." If you deserve it, it's not mercy.