“What does the apostle mean by ALL INIQUITY? When he says ALL, he excludes nothing: he comprehends sin, original and actual, and announces that we are redeemed from the penalty and guilt of all sin, considered as transgression of the divine law. The meaning is, that Christ redeemed us from sin, considered as guilt and entailing the curse of the law. Our great God and Savior transferred the curse to Himself. Free from personal guilt, He entered into the place of the guilty, and transferred their guilt to Himself, that we, in virtue of His sufferings, might be pronounced free of further obligation. His sufferings, might be pronounced free of further obligation. His sufferings had the quality of a compensation, price, or ransom paid for a captive; and this bloody ransom dissolved all connection between sin and our obligation to punishment, giving a right to liberty.
B. The second thing contemplated by the Lord in His death, was to PURIFY TO HIMSELF A PECULIAR PEOPLE. The two clauses, introduced by the same final participle, contain two different thoughts. The benefits expressed are equally connected with the cross. The idea conveyed by the term PURIFY is sacrificial. There are no fewer than six cognate terms—viz. PURIFY, SANCTIFY, SPRINKLE, SANCTIFY, WASH, CLEANSE—used by the apostles to point out the effect produced by sacrifice on those who were defiled by sin. The general sense attaching to them is this, that sinners, excluded by sin from a holy God, are freed from impurity and readmitted to fellowship with God by blood. That is the meaning of the term PURIFY in the passage now under consideration.
The counterpart of these things—redemption and purification—we find in Israel’s typical history. Redemption form Egypt was followed by the Sinaitic covenant, where the same people were taken into a new standing, as a kingdom of priests, to be a peculiar people to Himself (Deut. vii. 6). There is little doubt that Paul had his eye on that fact, and on the passages descriptive of it (Ex. xix. 5, 6). Christ’s people, redeemed by the true counterpart of the figurative covenant people. The apostle finely alludes to the redemption from Egypt, and then to entering into covenant with God at Sinai as a people sprinkled with blood, and henceforth near to Israel’s holy God (Ex. xxiv. 8). The design of that redemption was the consecration or setting apart of the nation to be a people near to Him; and the immediate effect of Christ’s redemption is to separate a people from the world, for holy service, or priestly worship. And the designations here applied to them are striking. They are called a PECULIAR PEOPLE, which means His OWN people, with the accessory idea of being a peculiar treasure, precious, and kept with care (Deut. xiv. 2, xxvi. 18). They are His treasure, held to be most precious.
Next, the additional designation, ZEALOUS FOR GOOD WORKS, assumes that they are partakers of the spirit of holiness (Rom. i. 4), and of the sanctification of the Spirit (1 Pet. i. 2). This comprehends the sober, righteous, and godly life already mentioned (ver. 12), as becomes men inhabited by the Spirit of God. They bear fruit, and zealously labor to bear it, as the end of their redemption, and as is worthy of a dedicated people.”
-From The Apostle’s Doctrine of the Atonement, by George Smeaton (first published 1879; by The Banner of Truth Trust, Carlisle, PA, 1991) Pages 330-331.