twelve cubits
Exodus 27:1
"And you shall make the altar of acacia wood, five cubits long and five cubits wide; the altar shall be square, and its height shall be three cubits.
2 Chronicles 4:1
Then he made a bronze altar, twenty cubits in length and twenty cubits in width and ten cubits in height.
Ezra 3:3
So they set up the altar on its foundation, for they were terrified because of the peoples of the lands; and they offered burnt offerings on it to the LORD, burnt offerings morning and evening.
square
Exodus 38:1
Then he made the altar of burnt offering of acacia wood, five cubits long, and five cubits wide, square, and three cubits high.
Exodus 38:2
He made its horns on its four corners, its horns being [of one piece] with it, and he overlaid it with bronze.