Inheritance in the kingdom of Christ and of God
Who are those that inherit the kingdom of God?
(I Corinthians 6:9-12 [KJV])  Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind,  Nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners, shall inherit the kingdom of God.  And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God.  All things are lawful unto me, but all things are not expedient: all things are lawful for me, but I will not be brought under the power of any.
The unrighteous shall not inherit the kingdom of God . But the believers have been washed in the blood of Christ . As a believer all things are lawful  but all things are not expedient.
(Romans 3:21-26 [KJV])  But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets;  Even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe: for there is no difference:  For all have sinned, and come short of the glory of God;  Being justified freely by his grace through the redemption that is in Christ Jesus:  Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God;  To declare, I say, at this time his righteousness: that he might be just, and the justifier of him which believeth in Jesus.
Who are the righteous? We see that we are justified freely by his grace through the dedemption that is in Christ Jesus , through faith in his blood , through faith in Jesus Christ .
(Ephesians 5:1-9 [KJV])  Be ye therefore followers of God, as dear children;  And walk in love, as Christ also hath loved us, and hath given himself for us an offering and a sacrifice to God for a sweetsmelling savour.  But fornication, and all uncleanness, or covetousness, let it not be once named among you, as becometh saints;  Neither filthiness, nor foolish talking, nor jesting, which are not convenient: but rather giving of thanks.  For this ye know, that no whoremonger, nor unclean person, nor covetous man, who is an idolater, hath any inheritance in the kingdom of Christ and of God.  Let no man deceive you with vain words: for because of these things cometh the wrath of God upon the children of disobedience.  Be not ye therefore partakers with them.  For ye were sometimes darkness, but now are ye light in the Lord: walk as children of light:  (For the fruit of the Spirit is in all goodness and righteousness and truth;)
So what does  mean that no whoremonger, nor unclean person, nor covetous man, hath any inheritance in God. What he is talking about is unbelievers, in other words lost people. Because the believers have been washed (1cor6:11) and therefore they are no longer defined by their sins.
(Revelation of John 20:11-15 [KJV])  And I saw a great white throne, and him that sat on it, from whose face the earth and the heaven fled away; and there was found no place for them.  And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works.  And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and they were judged every man according to their works.  And death and hell were cast into the lake of fire. This is the second death.  And whosoever was not found written in the book of life was cast into the lake of fire.
Unbelievers are thrown into the lake of fire  but the believers have their name written in the book of life  so they are not thrown into the lake of fire.
(Ephesians 1:13-14 [KJV])  In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise,  Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory.
Once saved always saved .