Ezekiel 43:12-13

And this is the basic law of the Temple: absolute holiness! The entire top of the mountain where the Temple is built is holy. Yes, this is the basic law of the Temple. “These are the measurements of the altar: There is a gutter all around the altar 21 inches deep and 21 inches wide, with a curb 9 inches wide around its edge. And this is the height of the altar