twelve cubits
Exodus 27:1
And thou shalt make an altar of shittim wood, five cubits long, and five cubits broad; the altar shall be foursquare: and the height thereof shall be three cubits.
2 Chronicles 4:1
Moreover he made an altar of brass, twenty cubits the length thereof, and twenty cubits the breadth thereof, and ten cubits the height thereof.
Ezra 3:3
And they set the altar upon his bases; for fear was upon them because of the people of those countries: and they offered burnt offerings thereon unto the LORD, even burnt offerings morning and evening.
square
Exodus 38:1
And he made the altar of burnt offering of shittim wood: five cubits was the length thereof, and five cubits the breadth thereof; it was foursquare; and three cubits the height thereof.
Exodus 38:2
And he made the horns thereof on the four corners of it; the horns thereof were of the same: and he overlaid it with brass.