Lets look at the context then: 29 Of how much worse punishment, do you suppose, will he be thought worthy who has trampled the Son of God underfoot, counted the blood of the covenant by which he was sanctified a common thing, and insulted the Spirit of grace?
So not referring to an unbelieving spouse. Context is clear.
I already looked at the context. In Hebrews 10:26, To "sin willfully" in the Greek carries the idea of deliberate intention that is habitual, which stems from
rejecting Christ deliberately. This is continuous action, a matter of practice. Now we don't walk along our daily life and "accidentally" fall into a pit called sin. We exercise our will but, the use of the participle clearly shows ongoing, willful action. The
unrighteous practice sin (1 Corinthians 6:9-10; Galatians 5:19-21);
not the righteous, who are born of God (1 Corinthians 6:11; 1 John 3:9).
As I already explained, if the word 'sanctified' in Hebrews 10:29 is used to describe saved people who lost their salvation as you teach, then we have a contradiction because the writer of Hebrews in verse 10 said
"sanctified through the offering of the body of Jesus Christ once for all" (Hebrews 10:10) and in verse 14, we read,
"perfected for all time those who are sanctified." (Hebrews 10:14)
*NOWHERE in the context does it specifically say the person who "trampled under foot the Son of God, and has regarded as unclean the blood of the covenant" was "saved" and/or "lost their salvation." The reference to "the blood of the covenant that sanctified him" in verse 29 "on the surface" appears to be referring to a Christian, but this overlooks the fact that the word translated "sanctified" (which is the verb form of the adjective "holy") which means "set apart," and doesn't necessarily refer to salvation, as I previously explained in regards to 1 Corinthians 7:14.
*In 1 Corinthians 7:14, Paul uses it to specifically refer to unbelievers who are "sanctified" or "set apart" by their believing spouse.
(And by this Paul does not mean that they are saved). A non-Christian can be "set apart" from other non-Christians without experiencing salvation as Paul explained. So the word "sanctified" means to be "set apart." If the word "sanctified" is to be given a broad brushed definition of saved, then you would have to say that the seventh day was saved (Genesis 2:3), the tabernacle was saved (Exodus 29:43), the Lord was saved (Leviticus 10:3), the Father saved the Son (John 10:36) and many other things that do not line up with scripture.
Once again, in verse 39, the writer of Hebrews sets up the
CONTRAST that makes it clear to me that he was referring to unbelievers, not saved people: But
WE are not OF THOSE who draw back to perdition, but
OF THOSE who believe to the saving of the soul. Those who
draw back to perdition do not believe to the saving of the soul and those who
believe to the saving of the soul do not draw back to perdition.
As I already explained, after considering the
CONTEXT of Hebrews 10, it seems most likely that "he was sanctified" should be understood in the sense of someone who had been "set apart" and was associated and identified with being an active participant in the Hebrew Christian community of believers, but later renounces their identification with these Hebrew believers, by rejecting the "knowledge of the truth" they had received (Hebrews 10:26) and trampling under foot the work and the person of Christ himself, which gives evidence that their identification with the Hebrew Christian community of believers "on the surface" had merely appeared to be real, but after closer examination turned out to be superficial and thus the person was not a genuine believer.