Passages must be understood in context. Each of these is a call for believers to repent from evil. They are not warnings about what will happen to unbelievers, but warnings concerning the result of sin in the lives of believers, believers shall not inherit the kingdom of God. And what is it that believers are to be seeking, are to be praying for? For the kingdom of God, will of God to be done on earth as it is in heaven!
1 Cor. 6:7 The very fact that you have lawsuits among you means you have been completely defeated already. Why not rather be wronged? Why not rather be cheated? 8 Instead, you yourselves cheat and do wrong, and you do this to your brothers and sisters. 9 Or do you not know that wrongdoers will not inherit the kingdom of God? Do not be deceived: Neither the sexually immoral nor idolaters nor adulterers nor male prostitutes nor practicing homosexuals 10 nor thieves nor the greedy nor drunkards nor slanderers nor swindlers will inherit the kingdom of God. 11 And that is what some of you were. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.
Paul is saying in context, stop suing your brother, and most certainly stop doing evil to your brother. You’ve been redeemed, freed from such evil and set apart to participate in the coming of the kingdom of God to earth! Don’t you know if you continue to sin you will not participate in the coming of the kingdom of God to earth!
Gal. 5:13 You, my brothers and sisters, were called to be free. But do not use your freedom to indulge the sinful nature; rather, serve one another humbly in love. 14 For the entire law is fulfilled in keeping this one command: “Love your neighbor as yourself.” 15 If you keep on biting and devouring each other, watch out or you will be destroyed by each other.
16 So I say, walk by the Spirit, and you will not gratify the desires of the sinful nature. 17 For the sinful nature desires what is contrary to the Spirit, and the Spirit what is contrary to the sinful nature. They are in conflict with each other, so that you are not to do whatever you want. 18 But if you are led by the Spirit, you are not under the law.
19 The acts of the sinful nature are obvious: sexual immorality, impurity and debauchery; 20 idolatry and witchcraft; hatred, discord, jealousy, fits of rage, selfish ambition, dissensions, factions 21 and envy; drunkenness, orgies, and the like. I warn you, as I did before, that those who live like this will not inherit the kingdom of God.
22 But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, 23 gentleness and self-control. Against such things there is no law. 24 Those who belong to Christ Jesus have crucified the sinful nature with its passions and desires. 25 Since we live by the Spirit, let us keep in step with the Spirit. 26 Let us not become conceited, provoking and envying each other.
Again, note that Paul is warning believers of the results of sin in their lives. If they continue to give in to the the flesh they will not participate in the kingdom of God which is righteousness, peace, and joy (love, joy, peace, perseverance, kindness, goodness, etc.). They will not inherit, participate in the kingdom of God coming to earth, in their lives much less anyone else’s!
By taking these passages out of context and interpreting them to be about some people getting into heaven some day (believers, saved) and others not (unbelievers, unsaved), such nullifies the power of these passages to call believers to repentance today! Reality is that sin brings death, destruction to believers and unbelievers alike, and it even hinders unbelievers from participating in the kingdom of God today!
Note that Mk. 10:17 is significantly different though it contains similar wording in “inherit”. It is spoken to a Jew, not a follower of Jesus. Jesus affirms him following the Law, and points out through His question the need that the man had, to love God and people more than money. And then Jesus, interestingly, speaks of how it is hard for a rich man to “enter” or “begin to experience” the kingdom of God, vs. 23! So Jesus equates “eternal life” with “beginning to experience the kingdom of God”!!!
Not one of these passages affirms ECT or even warns of such. They do warn that we, everyone, believer and unbeliever alike, must repent of sin and live right in order to participate in the kingdom of God today! To take these passages and somehow use them to affirm the certainty of damnation of others is to completely misinterpret and mishandle them. They are a call to repentace for those who believe in God, especially for we who claim to be disciples of Christ! If we give into the flesh then we shall not participate, enter in, or increase in the kingdom of God, the rule and reign of the Spirit, the righteousness, wholeness, and joy of being obedient to the reign of Christ!