King David said, "Blessed is the man to whom the Lord will not impute sin." What does that mean?

means that person has eternal salvation. And eternal salvation is the Gift of God, Romans 6:23 "Everlasting life is Eternal salvation" and it is a Bible doctrine, and a bible doctrine is part of Bible doctrine, 2 Ti 3:16 "all scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness": @ Ti 3:17 " that the man of God may be perfect, throughly furnished unto all good works."
North Red Bank Baptist Church, a Free Grace Church, "Holding forth the Word of Life" as Remnant Believers, seeking to reach all people with the Good News of Jesus Christ, Whom we preach, warning every man, and teaching every man in all wisdom, that we may present every man perfect {mature} in Christ Jesus: We look at current events in light of Biblical truth with a prophetic perspective.