“So it is God who decides to show mercy. We can neither choose it nor work for it” (Romans 9:16 NLT).

GOD’S MERCY AND MAN’S WILL AND WORKS
God shows mercy according to His own will and according to His own character. It is not in response to man’s will and works, yet this does not negate man’s responsibility. God shows mercy, not out of obligation, nor any indebtedness to humanity. For God’s mercy is an attribute of God’s character and is directed by God’s perfect will.
 
God’s mercy is on display in the cross of Christ. For God demonstrated His love and mercy toward us in that while we were still sinners, Christ died for us (Rom. 5:8). So, God did this not in response to us, but according to His own love and mercy. However, this message of the cross, which is the gospel, still requires a faith response from us in order to be recipients of God’s mercy.