Will God ever bring up a believer's sins again after forgiveness?
No. When a believer sins, forgiveness is immediate, and God will never come back to accuse them of still having sin on their ledger. The ledger has been wiped clean, and God's righteousness has been imputed to that believer's account.
Les teaches that if the Lord should come this very moment and a believer had done something wrong that forenoon and had not even had time to confess it, God would not bring it up and say that the believer sinned and had not taken care of it. The answer is no, because we are forgiven the moment we sin. Les explains that people find this hard to comprehend and say it is licensed, but it is not licensed; it is simply the grace of God that says God will never come back at us and accuse us of still having sin on our ledger. It has been wiped clean, and the whole bankroll of heaven has been put to our account—God's righteousness has been imputed to our account. Les also notes that the Old Testament economy of forgiveness and salvation is harder to delineate, though salvation existed there, and Paul can relate to it and even uses David as an example of faith.