Exodus 25:17 in the World English Bible
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.
Context
16 And thou shalt put into the ark the testimony which I shall give thee.
17 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.
18 And thou shalt make two cherubims of gold, of beaten work shalt thou make them, in the two ends of the mercy seat.