Ezekiel 43:16

And the altar hearth shall be twelve [cubits] long by twelve broad, square in the four sides of it.

Exodus 27:1

And thou shall make the altar of acacia wood, five cubits long, and five cubits broad (the altar shall be foursquare), and the height of it shall be three cubits.

Exodus 38:1-2

And he made the altar of burnt-offering of acacia wood: five cubits was the length of it, and five cubits the breadth of it, foursquare, and three cubits the height of it.

2 Chronicles 4:1

Moreover he made an altar of brass, twenty cubits the length of it, and twenty cubits the breadth of it, and ten cubits the height of it.

Ezra 3:3

And they set the altar upon its base, for fear was upon them because of the peoples of the countries. And they offered burnt-offerings on it to LORD, even burnt-offerings morning and evening.

Treasury of Scripture Knowledge

Summary

And the altar shall be twelve cubits long, twelve broad, square in the four squares thereof.

Square

Bible References

Twelve cubits

Exodus 27:1
And thou shall make the altar of acacia wood, five cubits long, and five cubits broad (the altar shall be foursquare), and the height of it shall be three cubits.
2 Chronicles 4:1
Moreover he made an altar of brass, twenty cubits the length of it, and twenty cubits the breadth of it, and ten cubits the height of it.
Ezra 3:3
And they set the altar upon its base, for fear was upon them because of the peoples of the countries. And they offered burnt-offerings on it to LORD, even burnt-offerings morning and evening.

Square

Exodus 38:1
And he made the altar of burnt-offering of acacia wood: five cubits was the length of it, and five cubits the breadth of it, foursquare, and three cubits the height of it.