Justification is God declaring sinners to be righteous in His sight.

"Yet God, in his grace, freely makes us right in his sight. He did this through Christ Jesus when he freed us from the penalty for our sins."
-Romans 3:24 NLT

"When people work, their wages are not a gift, but something they have earned. But people are counted as righteous, not because of their work, but because of their faith in God who forgives sinners."
-Romans 4:4-5 NLT