1 For the law, having a shadow of the good things to come, and not the very image of the things, can never with these same sacrifices, which they offer continually year by year, make those who approach perfect.
2 For then would they not have ceased to be offered? For the worshipers, once purified, would have had no more consciousness of sins.
3 But in those sacrifices there is a reminder of sins every year.
4 For it is not possible that the blood of bulls and goats could take away sins.
shadow (v.1) — the outline of an object
image (v.1) — the substance of an object
The tabernacle sacrifices were not of the same essence or image of Christ’s sacrifice, but were just a shadow or picture of it (v.1).
perfect (v.1) — complete (salvation)
worshipers (v.2) — servers, those bringing sacrifices
consciousness of sin (v.2) — consciousness of guilt for sin
reminder (v.3) — of sins committed since the previous sacrifice. The sacrifice itself (and the fact that it was needed) brought to mind the consciousness of sin.
The fact that the Old Testament sacrifices had to be repeated over and over showed that sin needed to be continually cleansed (v.3). They brought forgiveness, but not permanent forgiveness.
The figure of a promissory note might help here. Let us suppose one is in debt for a certain sum of money. He gives a note to run for a year. At the end of the year he finds himself unable to pay. He renews the note. The note has no real value in itself. Nor did the sacrifices have any moral or spiritual value in the sight of God. But in that note there is an acknowledgment of the debt from year to year. Now let us suppose some one who is well able to pay, endorses the note, what then? When it becomes due, it is referred to him for settlement and he discharges the obligation.
The application is simple and clear. It was not possible that the blood of bulls and of goats should take away sins; but every time a believing Israelite brought his sacrifice to the altar, he was, so to speak, giving his note to God. He acknowledged his indebtedness, his sin, and accepted responsibility for the same. This was all he could do, but the pre-incarnate Christ endorsed every one of the notes and in the fulness of time came prepared to settle in full for all. — Studies in the Epistle to the Hebrews, by H.A. Ironside, page 116.