Exodus 25:17 in the King James Version
And thou shalt make a mercy seat of pure gold: two cubits and a half shall be the length thereof, and a cubit and a half the breadth thereof.
Context
16 You shall put the covenant which I shall give you into the ark.
17 You shall make a mercy seat of pure gold. Two and a half cubits shall be its length, and a cubit and a half its width.
18 You shall make two cherubim of hammered gold. You shall make them at the two ends of the mercy seat.