One of the first principles of Biblical interpretation is that when there is a passage that is difficult to understand, interpretation of that passage must be informed by passages that are not difficult. In other words, the interpretation of an unclear passage must not disagree with the interpretation of a clear passage.
Specifically you asked if Hebrews 6 teaches that someone can lose their salvation. Here are the reasons why I do not think that Hebrews 6 teaches that you can lose your salvation:
- It goes against logic. If there is nothing that I can do to earn salvation, how could there be anything that I could do to cause me to lose it?
- It goes against Jesus’ teaching.
- “My sheep hear My voice, and I know them, and they follow Me; and I give eternal life to them, and they will never perish; and no one will snatch them out of My hand. “My Father, who has given them to Me, is greater than all; and no one is able to snatch them out of the Father’s hand.” (John 10:27–29, NASB) Never and no one are the function words in this statement. Never perish. No one can snatch them. By inference, the no one would include the person himself.
- John 3:16, 36 teach that whoever believes in Jesus has eternal life. To think that one could believe and then not believe is problematic. Once one knows something to be true, it is difficult for him to no longer know it.
- John 6:37 – “All that the Father gives Me will come to Me, and the one who comes to Me I will certainly not cast out.” (NASB) There is no out clause here but there is a beautiful in-clause.
- It goes against Paul’s teaching.
- Romans 8:1 – No condemnation for those who are in Christ Jesus
- Romans 8:35-39 – “Who will separate us from the love of Christ? Will tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword? Just as it is written, “For Your sake we are being put to death all day long; We were considered as sheep to be slaughtered.” But in all these things we overwhelmingly conquer through Him who loved us. For I am convinced that neither death, nor life, nor angels, nor principalities, nor things present, nor things to come, nor powers, nor height, nor depth, nor any other created thing, will be able to separate us from the love of God, which is in Christ Jesus our Lord.” (NASB) NOTHING can separate us from the love of God.
- “In Him, you also, after listening to the message of truth, the gospel of your salvation—having also believed, you were sealed in Him with the Holy Spirit of promise, who is given as a pledge of our inheritance, with a view to the redemption of God’s own possession, to the praise of His glory.” (Ephesians 1:13–14, NASB) We are sealed when we come to faith as a promise of the inheritance we will receive.
I could keep adding verses to these, but you get the point. These verses clearly present the truth that if we truly come to faith in Jesus, we do not have to worry that we can lose our salvation.
So then, what is Hebrews 6 saying?
If you look at the language in Hebrews 6:4-6, it does not openly declare that the author is speaking about someone who has experience new birth. Most commentators understand these verses to describe someone who has been part of the church and has experienced some of the blessings of being in the group without coming to saving faith. If you can see the work of God in others’ lives and experience the goodness of God and still walk away, it is unlikely that such a one will ever return. We should not be surprised to find unbelievers in the church. Jesus gave us the parable of the wheat and the tares to illustrate this. Also in Matthew 7:26-27 Jesus tells us, “Everyone who hears these words of Mine and does not act on them, will be like a foolish man who built his house on the sand . . . “