Yea, Barclay's daily bible commentary is great. From my point of view, the issue is that he is reading Hebrews like it was written to himself and all Christians through all of time. The historical significance seems to be lost. Even the site Biblica says:Hebrews must have been written before the destruction of Jerusalem and the temple in a.d. 70 because: (1) If it had been written after this date, the author surely would have mentioned the temple’s destruction and the end of the Jewish sacrificial system; and (2) the author consistently uses the Greek present tense when speaking of the temple and the priestly activities connected with it (see5:1–3; 7:23,27; 8:3–5; 9:6–9,13,25; 10:1,3–4,8,11; 13:10–11).
Now I don't know about the Greek stuff, but surely the author would have made mention that this sacrificial system WAS as in 'used to be' before the temple destruction. I kind of think that Hebrews was written to the Hebrews.
As a side note, I remember a Free Will Baptist pastor sitting at my kitchen table and using these very verses to try to convince me that the 'once saved always saved' doctrine was rubbish.
Having said that Barclay does end with this:
We may note a final thing. It has been pointed out that in the letter to the Hebrews there are four impossible things. There is the impossibility of this passage. The other three are: (i) It is impossible for God to lie (Hebrews 6:18). (ii) It is impossible that the blood of bulls and goats should take away sin (Hebrews 10:4). (iii) Without faith it is impossible to please God (Hebrews 11:6).