The phrase "rich in mercy" comes from Ephesians 2:4 and is a counterbalance to the description of humanity being rich in sin. Only a God rich in mercy would conceive a plan to save and redeem such wicked creatures. Mercy is compassion or forgiveness extended to someone who deserves punishment or harm. Mercy is undeserved pardon. Mercy is the only explanation for Christ’s great sacrifice on our behalf (2 Corinthians 5:21).
People can show mercy to one another on a limited, human basis. But our offenses against God were so heinous, so unforgivable, that His forgiveness shows Him to be more than merciful—He is rich in mercy. A God rich in mercy “demonstrates his own love for us in this: While we were still sinners, Christ died for us” (Romans 5:8). Before we cared or knew Him, God had already extended mercy toward us.
1 Peter 1:3 counters any tendency to believe that our salvation is due to some merit within ourselves:
“Praise be to the God and Father of our Lord Jesus Christ! In his great mercy he has given us new birth into a living hope through the resurrection of Jesus Christ from the dead.”
As we continue on in our Christian walk, God is still faithful to cleanse and purify us of all sins (1 John 1:9). He is patient with us (2 Peter 3:9). Only God is able to forgive our sins, and there is good news for us: “The Lord is gracious and full of compassion, slow to anger and great in mercy. The Lord is good to all, and His tender mercies are over all His works.” (Psalm 145:8-9). We can put our hope in God with confidence, knowing that even when we make mistakes, He will still be rich in mercy toward us.