John Calvin on Exodus 25:17

17 And thou shalt make a mercy-seat. The primary root of the verb כפר, caphar, from whence this noun is derived, כפרת C. has not derived his explanation of the verb כפר from his usual guide in Hebrew, viz., S.M.; but his remark, that it signifies to smear over with bitumen, or pitch, agrees with its generally acknowledged meaning in Genesis 6:14. It is in the Pihel conjugation, — the effect of which is frequently the same as that proper to the Hiphil, — that the verb means to expiate. The noun, as C. observes, properly signifies a covering. — W. is used for “to smear with pitch,” but in the Hiphil conjugation, it signifies either to expiate, or to purge, or to receive into favor; whence כפר, copher, is expiation, as we have seen elsewhere; and כפרת, caphoreth, a covering or lid. Yet I doubt not but that Moses alludes in this word to a metaphorical meaning, for the law requires a covering to conceal our transgressions. And it is probable that, when Paul calls Christ ἱλαστήριον, (Romans 3:25,) and John ἱλασμὸν, (1 John 2:2,) they both refer to this figure, because God was propitiated towards believers by the covering of the Law, so as to shew Himself favorable to them by hearing their vows and prayers. For as long as the law stands forth before God’s face it subjects us to His wrath and curse; and hence it is necessary that the blotting out of our guilt should be interposed, so that God may be reconciled with us. Nor is it without reason that David exclaims, after he has proclaimed the righteousness of the law, “Who can understand his errors?” (Psalm 19:12.) Whence we gather that, without a propitiation, the law does not bring us near to God, but accuses us before Him. And assuredly, when I consider all things, it seems to me a tame explanation, that Moses spoke literally of the cover, when he Addition in Fr., “quand il le magnifie tant, et." would have the Cherubim turn their faces toward it, and God promises that He will give His answers from it. By these honorable distinctions it is exalted above the Ark.