The first mention of not inheriting the kingdom of God is found in Paul’s first letter to the church at Corinth. “Do you not know that the wicked will not inherit the kingdom of God? Do not be deceived: Neither the sexually immoral nor idolaters nor adulterers nor male prostitutes nor homosexual offenders nor thieves nor the greedy nor drunkards nor slanderers nor swindlers will inherit the kingdom of God" (1 Corinthians 6:9-11).
By saying the wicked will not inherit the kingdom of God, Paul is stating that the wicked are not children of God, nor are they heirs of eternal life (Romans 8:17). This does not mean that anybody who has ever committed one of these sins will be denied entrance to heaven. What differentiates a Christian’s life from that of a non-Christian is the struggle against sin and the ability to overcome it. A true Christian will always repent, will always eventually return to God, and will always resume the struggle against sin. But the Bible gives no support for the idea that a person who perpetually and unrepentantly engages in sin can indeed be a Christian. The 1 Corinthians passage lists sins that, if indulged in continuously, identify a person as not being redeemed by Christ.
The Christian’s response to sin is to hate it, repent of it, and forsake it. We still struggle with sin, but by the power of the Holy Spirit who lives in us, we are able to resist and overcome sin. The hallmark of a true Christian is the decreasing presence of sin in his life. As Christians grow and mature in the faith, sin has less and less of a hold on us. Of course, sinless perfection is impossible in this life, but our hatred for sin becomes greater as we mature. Like Paul, we are distressed that sin still exists in our flesh, causing us at times to do what we don’t want to do and looking to Christ for relief from this “body of death” (Romans 7:18-25).
If a person actively, perpetually, and unrepentantly lives a homosexual lifestyle, the lifestyle of a thief, a greedy lifestyle, a drunken lifestyle, etc., that person is showing himself to be unsaved, and such a person will definitely not inherit the kingdom of God.