I need help in clarifying justification as Protestants account for it.
I'm a sinner, and I'd like to one day enter heaven. But heaven cannot contain sin, therefore if I am to enter heaven, I am to be without sin.
How then will imputed righteousness be sufficient in allowing me to enter heaven? It seems I would need to be actually internally changed, or infused with Christ's righteousness if I'm even to last one moment in Heaven.
Please stay on topic. I know questioning forensic justification leads to Catholicism, but I'd really like to just understand who Christians are able to enter heaven with imputed righteousness alone. All popery and anti-Catholic replies should be ignored and avoided.
What happened when you accepted Christ as Saviour, the act of taking your sin on the cross with Him became a reality for you. Jesus was totally righteous when He went to the cross, but He took the sinfulness, guilt, and punishment for sin for everyone who has and will embrace Him. This means that as far as God is concerned, all your sin, past present and future has been transferred to Christ, and His righteousness has been transferred to you. This means that God no longer sees you as a sinner, even a forgiven one. You are much more than that. You are now born of God, a new creation in Christ. This also means that because of the resurrection of Christ, you received eternal life as soon as you took Him as your Saviour. This means that when you die, you will go straight into the presence of the Lord. You won't receive a new after-life, because you already have eternal life right now.
When your body dies, you will leave the sinful shell behind and enter into glory as the person you really are. You live in your body with its shortcomings and failures. There will always be a conflict between the new life within you and the limitations of your body. But it will be your body shell that will fall away at death, but the real you with your new life will go into glory. When you stand before Christ in glory, there will be no sin in you. The last vestiges of that in your body will have been left behind to moulder in the grave.
At the last day, when the dead in Christ will arise, you will be raised in a glorified, sinless body, just like Jesus was raised the same way. He is the first-born of many brethren. Because He rose from the dead, so will you in the same way.
So, to summarise; you are already totally righteous in God's sight. The moment you received Christ, God took your sins and buried them in the deepest sea of His forgetfulness. Jesus is a complete Saviour, not a partial one, therefore your righteousness in Christ is total, complete. You have a new heart and your spirit is alive to God. It is your body that holds you back and makes you feel like you are still a sinner. Therefore you need to view yourself as born of God and totally righteous before Him.
The Scripture says, "I am crucified with Christ, nevertheless I live, yet not I, but Christ lives in me; and the life I live I live by the faith of the Son of God who loves me and gave Himself for me."