Thou shalt make a mercy seat. Modern exegesis has endeavoured to empty the word kapporeth of its true meaning, witnessed to by the Septuagint, as well as by the Epistle to the Hebrews (Hebrews 9:5). It tells us that a kapporeth is simply a cover, "being derived from kaphar, to cover,"—used in Genesis 5:14, with respect to covering the ark with pitch.
But the truth is that kapporeth is not derived from kaphar, but from kipper, the Piel form of the same verb, which has never any other sense than that of covering, or forgiving sins. In this sense it is used in the Old Testament some seventy times.
Whether the mercy seat was the real cover of the ark of the covenant, or whether that had its own lid of acacia wood, as Kalisch supposes, is uncertain. At any rate, it was not called kipporeth because it was a cover, but because it was a seat of propitiation.
On the importance of the mercy seat, as in some sort transcending the ark itself, see Le Genesis 16:2, and 1 Chronicles 28:11. Atonement was made by sprinkling the blood of expiation upon it (Le 1 Chronicles 16:14, 1 Chronicles 16:15).
Of pure gold, Not of wood, plated with metal, or richly gilt, but of solid gold—an oblong slab, three feet nine inches long, two feet three inches wide, and probably not less than an inch thick. The weight of such a slab would be above 750 lbs.
troy, and its value above 25,000l. of our money. The length and breadth were exactly those of the ark itself, which the mercy seat thus exactly covered (1 Chronicles 28:10).