In Hebrews 6:4-6 it says “For concerning those who were once enlightened and tasted of the heavenly gift, and were made partakers of the Holy Spirit, and tasted the good word of God, and the powers of the age to come, and then fell away, it is impossible to renew them again to repentance; seeing they crucify the Son of God for themselves again, and put him to open shame.” Does this mean people can lose their salvation? If not, what does it mean?
There are two facets to our relationship with God. There is union, which happens at the moment of salvation and guarantees our eternity with Him (2 Cor. 1:21-22, 2 Cor. 5:5, Ephes. 1:13-14, Ephes 4:30) and there is fellowship, the ability to dwell in His presence and communicate with Him in the here and now (John 15:4-5). Union is unconditional and is based on our belief. Fellowship is conditional and is based on our behavior.
The context of Hebrews 6 is interrupting our fellowship with God, not breaking our union. The key is the phrase “renew again to repentance.” Jewish believers were being pressured into keeping the law, especially where it concerned the daily sacrifice for sin. Those who relied on the daily sacrifice instead of invoking 1 John 1:9 (confessing directly to God) were in effect crucifying the Lord all over again, since He is the Lamb of God who takes away the sin of the world. The daily sacrifice was a foreshadowing of Him, and when He came the shadow gave way to the reality. The old way was no longer sufficient to restore them to fellowship (Hebr. 10:1-18).
Since 1 John 1:9 says that confession brings forgiveness and purification from all unrighteousness (renewal again to repentance), then by implication anything other than confessing our sins prevents forgiveness and purification and causes estrangement from God. It doesn’t revoke our salvation, but because God can’t be in the presence of sin, it does suspend our relationship, depriving us of blessings we could have otherwise had.
There are many clear verses that unequivocally promise eternal security. Since the Bible cannot contradict itself and still be the Word of God, interpreting Hebrews 6 as having anything to do with salvation is a violation of the rules of interpretation, which teaches that we’re to use clear verses to interpret obscure ones, not the other way around.