6:4 JESUS’ offering ‘Once for All’ Heb 7:27, 9:26, 10:10 - could be seen as a one time offer for believers with no returning from failures as Heb 6:4 seems at first to indicate “once enlightened” ‘if they fall away, it is impossible to renew them’.... Any self imposed perfection never resulted in a perfect group of pure believers - Guilt and shame must have poured out after every Day of Atonement rather than Mercy and Forgiveness. Doubts and accusations must have been constant reminders from ‘The Accuser of The Brethren.’ 1Corinthians 5:1-3 shows a man who was dis-fellow-shipped because he had his father’s wife. Yet he seems to have been reconciled in 2Cor 2:5-11. Thus there is a way that leads to salvation and that way is found in Christ Jesus alone and in His fulfilment of God’s Eternal Salvation Plan. Peter is a wonderful example, he often falls short but he is always lifted back up again....
‘Two Immutable Things’ 6:18 most likely - The ‘two immutable things’ refers to the previous verses regarding Abraham: Where both God’s Promise and His Oath were given to Abraham due to Faith. The whole of it brings us to depending on JESUS as ‘our forerunner’ and GOD as our Father. (Abraham is only a temporary character and only mentioned in Hebrews Chapter 6 in verse 13, while JESUS is central and pre-eminent in the whole of Hebrews.) If we look at Abraham, he too fell short but God provided Faith to fulfill the promises....
6:19 JESUS entered into GOD’s Presence ‘The Innermost behind the curtain’, deals with The Day of Atonement - JESUS removes the guilt, gives Mercy and provides Access to GOD. Fulfilling the O T Pattern for Atonement. Thus the end of Chapter 6 brings us again to JESUS and away from focusing on doctrine. Doctrine can be good but Jesus is Perfect....
6:1-4 THEREFORE LET US go on and get past the elementary stage in the teachings and doctrine of Christ (the Messiah), advancing steadily toward the completeness and perfection that belong to spiritual maturity. Let us not again be laying the foundation of repentance and abandonment of dead works (dead formalism) and of the faith [by which you turned] to God, 2 of the doctrine of baptisms, of laying on of hands, of resurrection of the dead, and of eternal judgment. 3 And this we will do if God permits. 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, AMPLIFIED
6:1-4 Therefore, having put away once for all the beginning word of the Messiah [the first testament in animal blood, i.e., the Mosaic economy], let us be carried along to that which is complete [the new testament in Jesus’ blood], not again laying down a foundation of repentance from dead works, and of faith toward God, of the teaching of ablutions, and of imposition of hands, of a resurrection of the dead, and of eternal judgment [doctrines of the Mosaic economy]. And this will we do if only God permits, for it is impossible in the case of those who have been once for all enlightened, and have both tasted of the heavenly gift and have become companions of the Holy Spirit [willingly being led along towards the act of faith in the pre-salvation work of the Holy Spirit], WUEST
These 2 Translations lead to very different Conclusions about Chapter 6.
The WUEST Translation seems better to support the concluding idea -
' they cannot be renewed to salvation... they Crucify Christ again...' 6:4-6
Paul also says the same concept-- when believers seek to return to Old Testament works - including Circumcision- Christ shall profit you nothing Gal 5:2
Also, the 7 doctrines listed in Verses1-3, when translated by Wuest, Support the remainder of The New Testament .