Albert Barnes Commentary 1 Kings 7:15

"For he fashioned the two pillars of brass, eighteen cubits high apiece: and a line of twelve cubits compassed either of them about." — 1 Kings 7:15 (ASV)

These famous pillars, which were broken to pieces by the Babylonians when they destroyed Jerusalem (2 Kings 25:13; Jeremiah 52:17), were likely ornamental, standing by themselves under or in front of the porch. The Phoenicians were known to use isolated metal columns as sacred ornaments, so Hiram would have been familiar with this type of decoration.

The shaft alone appears to have been eighteen cubits high. Adding the capital (1 Kings 7:16, 19), the entire metal pillar was 27 cubits high. If it also had a stone base of eight cubits—which would not be greatly out of proportion—the total height of 35 cubits mentioned in 2 Chronicles 3:15 would have been reached. For comparison, some columns at Persepolis are 67 feet high. The pillar's circumference of 12 cubits (18 feet) implies a diameter of about 5 feet 9 inches at the base, which would make it appear somewhat heavy. Egyptian pillars, however, were even thicker in proportion to their height.

On the assumption that a portion of the original text has been lost, the verse has been reconstructed as follows: “He cast two pillars of brass; eighteen cubits was the height of the one pillar, and eighteen cubits was the height of the other pillar; and a line of twelve cubits compassed the one pillar, and a line of twelve cubits compassed the other pillar.”