Thank you for your patience and faithfulness in sticking with this topic, but it is too important a subject to cut it short. Thank you.
Read Hebrews 10 again, if time permits.
The careless Christian starts to drift through neglect; then he doubts the Word; then he grows dull toward the Word; and the next step is deliberately sinning and despising his spiritual heritage. Note the important facts about this particular sin.
It is not one sin committed once; “sin willfully” in verse 26 it means he “willingly goes on sinning.” It is the same continuous tense of the verb as in 1 John 3:4-10 – “Whosoever continually and habitually sins are not born of God.”
So, this passage is not dealing with an “unpardonable sin;” it is talking about an attitude toward the Word of God that God calls willful rebellion.
There were no sacrifices in the Old Testament for deliberate, presumptuous sins (see Exodus 21:14; Numbers15:30). Sins of ignorance (Leviticus 4) and of sudden passion were covered; but willful sins merited only punishment.
Verse 29 reminds us that our salvation (and the shed blood that purchased it) are held in high regard by God. The Father values His Son; the Son shed His blood; the Spirit applies the merits of the cross to the believer.
For us to sin willfully is to sin against the Father, Son, and Spirit. Paul quotes Deuteronomy 32:35-36 to show that God, in the Old Testament, saw to it that His people (not unbelievers) reaped what they sowed and were judged when they disobeyed willfully.
The fact that they were His covenant people made their obligations that much greater (Amos 3:2). God judges His people: Romans 2:16; 1 Corinthians 11:31-32; 1 Peter 1:17, etc. Of course, this is not eternal judgment, but rather His chastening in this life, and loss of reward in the next.
Note verses 34-35 where the emphasis is on reward for faithfulness, not salvation. See also 1 Corinthians 3:14-15; 5:5; 9:27; 11:30