Yes, v. 26 is about those who reject Christ, those who count His blood a common thing after having been sactified by it (v. 29). You can’t just change the author’s subject willy-nilly to make him say what you want him to.
If your view is correct then the writer contradicts himself and a lot of the NT regarding the eternal security of the believer. I don't see that happening here.
It flies against this:
Jesus said: Truly, truly, I say to you, he who hears My word, and believes Him who sent Me, has eternal life, and does not come into judgment, but has passed out of death into life. (John 5:24)
On your security in Him: My sheep hear my voice, and I know them, and they follow Me; and I give eternal life to them, and they shall never perish; and no one shall snatch them out of My hand. (John 10:27-28)
On your homepage you note you are a Christian.....do you believe you can lose your eternal security?
If so, why?
What must you do to keep it?
Just as with Israel out of Egypt, God delivered His saints from the bondage of sin with a mighty hand. He provided the Lamb Whose blood spared them from the wrath, and the water that drowned their pursuers is the water by which He saved them.
As they trudge through the wilderness, He provides for them, giving them bread day by day to teach them that "man shall not live by bread alone, but by every word that proceeds from the mouth of God." (The bread comes because God orders it to.) The water that comes from the Rock in the desert is from Christ Himself.
All these things are to teach us to rely not on ourselves, but on God.
The Israelites did not rely on God, but defied and departed from Him to serve other gods, having "an evil heart of unbelief, in falling away from the living God," even after being the benificiaries of His mighty deliverance. Time and again God sent judgments upon them for their rebellions and defiant grumblings. This is the illustration the Hebrews writer holds up as a warning to the saints:
"Wherefore I was displeased with this generation, And said, They do always err in their heart: But they did not know my ways; As I sware in my wrath, They shall not enter into my rest.
Therefore, as the Holy Spirit says:
'Today, if you will hear His voice,
Do not harden your hearts as in the rebellion,
In the day of trial in the wilderness,
Where your fathers tested Me, tried Me,
And saw My works forty years.
Therefore I was angry with that generation,
And said, "They always go astray in their heart,
And they have not known My ways."
So I swore in My wrath,
"They shall not enter My rest."'
Beware, brethren, lest there be in any of you an evil heart of unbelief in departing from the living God; but exhort one another daily, while it is called 'Today,' lest any of you be hardened through the deceitfulness of sin. For we have become partakers of Christ if we hold the beginning of our confidence steadfast to the end, while it is said:
'Today, if you will hear His voice,
Do not harden your hearts as in the rebellion.'
For who, having heard, rebelled? Indeed, was it not all who came out of Egypt, led by Moses? Now with whom was He angry forty years? Was it not with those who sinned, whose corpses fell in the wilderness? And to whom did He swear that they would not enter His rest, but to those who did not obey? So we see that they could not enter in because of unbelief." - Heb. 3:7-19
The point of reminding his readers of this story which they knew so well is to warn them lest the same thing happen to them. The Israelites were delivered from bondage, but yet were denied entrance into the Promised Land. Because God was unfaithful? No, but because THEY were. Because God was impotent? No, but because THEY fell away and departed from Him.
Let all Christians beware, lest the same thing happen to us. Paul uses this same illustration in
1 Cor. 10. But rather than take up even more space with this post, let me cite only his "therefore" conclusion from v. 12:
"Therefore let him who thinks he stands take heed lest he fall."