And from the base upon the ground to the lower ledge shall be two cubits, and the width one cubit; and from the smaller ledge even to the larger ledge shall be four cubits, and the width one cubit.
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George Leo Haydock
Cubit. They were each a cubit broad, but this greater means higher up. Some assert that the priests stood on this base to avoid treading on the altar, when they placed the wood or victims. But it would be too low; and steps were made for that purpose. The altar was ten, or rather twelve cubits high, and as many broad. Solomon's was ten high and twenty broad. Herod's was a square of forty cubits, raised fifteen from the ground. (Calmet)