Deuteronomy is the Old Covenant. Very different from the New Covenant.
Salvation is the New Covenant. So your Deuteronomy verses are not proof text for the New Testament as far as if salvation can be lost. It is VERY CLEAR that Jesus says that the New Covenant is a NEW AND BETTER COVENANT than the Old Covenant.
The fact that you even mention Hebrews 10:26-29 when we have had this conversation about this verse 5 times is quite frustrating.
Hebrews 10
1For since the law has but a shadow of the good things to come instead of the true form of these realities, it can never, by the same sacrifices that are continually offered every year, make perfect those who draw near.
2Otherwise, would they not have ceased to be offered, since the worshipers, having once been cleansed, would no longer have any consciousness of sins?
3But in these sacrifices there is a reminder of sins every year.
4For it is impossible for the blood of bulls and goats to take away sins.
5Consequently, when Christ
a came into the world, he said,
“Sacrifices and offerings you have not desired,
but a body have you prepared for me;
6in burnt offerings and sin offerings
you have taken no pleasure.
7Then I said, ‘Behold, I have come to do your will, O God,
as it is written of me in the scroll of the book.’”
8When he said above, “You have neither desired nor taken pleasure in sacrifices and offerings and burnt offerings and sin offerings” (these are offered according to the law),
9then he added, “Behold, I have come to do your will.” He does away with the first in order to establish the second.
10And by that will we have been sanctified through the offering of the body of Jesus Christ once for all.
11And every priest stands daily at his service, offering repeatedly the same sacrifices, which can never take away sins.
12But when Christ
b had offered for all time a single sacrifice for sins, he sat down at the right hand of God,
13waiting from that time until his enemies should be made a footstool for his feet.
14For by a single offering he has perfected for all time those who are being sanctified.
15And the Holy Spirit also bears witness to us; for after saying,
16“This is the covenant that I will make with them
after those days, declares the Lord:
I will put my laws on their hearts,
and write them on their minds,”
17then he adds,
“I will remember their sins and their lawless deeds no more.”
18Where there is forgiveness of these, there is no longer any offering for sin.
The Full Assurance of Faith
19Therefore, brothers,
c since we have confidence to enter the holy places by the blood of Jesus,
20by the new and living way that he opened for us through the curtain, that is, through his flesh,
21and since we have a great priest over the house of God,
22let us draw near with a true heart in full assurance of faith, with our hearts sprinkled clean from an evil conscience and our bodies washed with pure water.
23Let us hold fast the confession of our hope without wavering, for he who promised is faithful.
24And let us consider how to stir up one another to love and good works,
25not neglecting to meet together, as is the habit of some, but encouraging one another, and all the more as you see the Day drawing near.
26For if we go on sinning deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, 27but a fearful expectation of judgment, and a fury of fire that will consume the adversaries. 28Anyone who has set aside the law of Moses dies without mercy on the evidence of two or three witnesses. 29How much worse punishment, do you think, will be deserved by the one who has trampled underfoot the Son of God, and has profaned the blood of the covenant by which he was sanctified, and has outraged the Spirit of grace?
30For we know him who said, “Vengeance is mine; I will repay.” And again, “The Lord will judge his people.”
31It is a fearful thing to fall into the hands of the living God.
Reading Hebrews 10, you will see that it is talking about Old Testament and the temporary sacrifice for sin that the Levitical priesthood performed. That is the sacrifice for sin that is no longer acceptable. The temporary atonement of sin through animal sacrifice. But you know this. And you used it anyway. That is dissapointing that you are not taking the opportunity to correct your mistranlations and understanding. Shame.
