An adaptation of the Catechism for Young Children in modern English.
Question: What is justification?
Answer: It is God forgiving sinners and treating them as if they had never sinned.
Question: What is justification?
Answer: It is God’s forgiving sinners, and treating them as if they had never sinned.
Smoothing “God’s” to simply “God”, and removing an extraneous comma to connect the clauses.