What about Hebrews 6:4-6?
A : Hear what the Scripture says, "4 For it is impossible for those who were once enlightened, and have tasted the heavenly gift, and have become partakers of the Holy Spirit, 5 and have tasted the good word of God and the powers of the age to come, 6 if they fall away, to renew them again to repentance, since they crucify again for themselves the Son of God, and put Him to an open shame. 7 For the earth which drinks in the rain that often comes upon it, and bears herbs useful for those by whom it is cultivated, receives blessing from God; 8 but if it bears thorns and briers, it is rejected and near to being cursed, whose end is to be burned." (Heb 6:4-8).
Here in Heb 6:4-8, we can see if a believer chooses to sin willfully it brings shame to the glorious name of the Lord and not only that, it again says that it is very hard for them to renew them to repentance as they are crucifying the Son of God and are putting Him to open shame. If they are not saved really, they cannot put the name that they represent to open shame. This shows that they were saved people. But when they are not able to repent the following verses says, the saved believer will not receive a blessing from God. Their lives will become fruitless and then the writer says that they are near to being cursed, Why? Because they have been truly saved and redeemed by the Lord Jesus, even though they lived a fruitless lives just because of His goodness they were not cursed fully to hell fire which they fully deserve. Those who are cursed fully will end up in none other place than eternal hell fire. The unrepentant believer were not cursed fully to go to hell because Jesus took all the curses on behalf of them on the Cross of Calvary (Gal 3:13). The life of a unrepentant believer will have no God's blessing upon it now and also in the area of the rewards that follows it for eternity ahead. All their works of religiosity done without a good motive to please the Lord will be completely burnt off in the end, but they themselves and their soul will be saved because of what Jesus had achieved for them on the Cross (1 Cor 3:15; John 19:30; Heb 10:12, 14).
Unrepentant heart for a believer in itself is a judgment and punishment of God that has come upon that person for his wilful attitude towards sin's pleasure (Heb 10:30-31). God chastises his sinning children now along with the world so that they might not be condemned with the world in the after life (2 Peter 2:5; 1 Peter 4:5-6, 17-18; 3:18-20). God judges His people along with the world physically so that He might justify them spiritually from eternal condemnation (1 Cor 5:5). Ooo, I praise the Lord for the goodness of God shown to the children of men! This affirms that the salvation of God is eternal in nature (Heb 5:9). Once saved is always saved as long as a person is truly saved. These Scriptures have to be taken out of context to justify that a person loses his or her salvation when willful sinning happens. Praise the Lord! Much Blessings.....