St. Paul teaches that salvation is achieved through God and a person working together. Salvation comes from God alone (Catechism of the Catholic Church, paragraph 169), but is not achieved by God alone. The person must respond to God’s offer by accepting God’s invitation to dwell in and work through the person.
Jesus clearly and repeatedly taught that salvation is obtained by participating with God. For example, in Mark (10:17-21) Jesus tells the man who asks what he should do to achieve salvation to follow the commandments, sell what he has, give the money earned from the sale to the poor, and come, follow Him. Each of these requires an action (work) on the man’s part – follow the commandments, sell what he has, give the proceeds of the sale to the poor, and come, follow Jesus.
Salvation comes to a person from accepting God’s invitation to dwell in and work through the person. For example, Paul teaches (Galatians 2:20), “And I live, now not I: but Christ lives in me. And that I live now in the flesh: I live in the faith of the son of God, who loved me and delivered himself from me.” Paul further writes (2 Corinthians 6:1), “Working together with Him, then, we entreat you not to accept the Grace in God in vain.