Isa 55:7 Let the wicked forsake his way, and the unrighteous man his thoughts: and let him return unto the LORD, and he will have mercy upon him; and to our God, for he will abundantly pardon.

Prepare the way of the Lord by repenting of both kinds of sin, let him return to the Lord, and he will have mercy upon him, and abundantly pardon.

How does one 'return' to the Lord? It is implied that he was once with the Lord. When was this? Paul has correctly deduced that he was once alive without the law, and then the law came and he died.