Eph 2 explains it all so well:
"And you did he make alive, when ye were dead through your trespasses and sins, wherein ye once walked according to the course of this world, according to the prince of the powers of the air, of the spirit that now worketh in the sons of disobedience; among whom we also all once lived in the lusts of our flesh, doing the desires of the flesh and of the mind, and were by nature children of wrath, even as the rest:— but God, being rich in mercy, for his great love wherewith he loved us, even when we were dead through our trespasses, made us alive together with Christ (by grace have ye been saved), and raised us up with him, and made us to sit with him in the heavenly places, in Christ Jesus: that in the ages to come he might show the exceeding riches of his grace in kindness toward us in Christ Jesus: for by grace have ye been saved through faith; and that not of yourselves, it is the gift of God; not of works, that no man should glory. For we are his workmanship, created in Christ Jesus for good works, which God afore prepared that we should walk in them."
The dead sinner must be given new life, along with that goes the free gift of eternal life. And we get this guarantee:
Thou shalt call His name Jesus, for He shall save His people from their sins.
Stubborn persistent willful sin on the part of a Christian results in chastisement, possibly even to the point of physical death that the spirit may be saved. But nothing, but nothing will separate the child of God from that special love in Christ Jesus. King David is an extreme example of sin, but even he did not get to the point that he had to be executed.
Nothing present and nothing in the future can separate the believer from the special love which they have in Christ Jesus. "I give them eternal life, and they shall never perish."
He has paid for all the Christian's sins.
He has redeemed us at the cost of His precious blood.
You surely have heard all this before.
May the Lord open blind eyes to realize how hopeless is a man's case apart from God's grace. May those who trust in their supposed good works, repent of the sin of the Pharisee, self-righteousness. He came not to call the righteous, but sinners.