Albert Barnes Commentary 1 Kings 7:2

"For he built the house of the forest of Lebanon; the length thereof was a hundred cubits, and the breadth thereof fifty cubits, and the height thereof thirty cubits, upon four rows of cedar pillars, with cedar beams upon the pillars." — 1 Kings 7:2 (ASV)

Many have supposed that the buildings mentioned in 1 Kings 7:1–2 and 1 Kings 7:8 were three entirely distinct and separate structures. However, it is perhaps better to view them as an interconnected complex.

In this view, the "house" of 1 Kings 7:1 was the palace proper—Solomon’s own residence (see 1 Kings 7:8). The house in 1 Kings 7:2 served as the state apartments, and the house for Pharaoh’s daughter was the women's quarters. These three groups of buildings, while distinct, were interconnected and together formed what is elsewhere called "the king’s house" (1 Kings 9:10).

The House of the Forest of Lebanon. This name was likely given because its main feature—a mass of cedar pillars—was thought to resemble the cedar forests of Lebanon. Its length of "a hundred cubits," or 150 feet, was nearly twice that of the entire temple, excluding the porch. For comparison, some great halls in Assyrian palaces were occasionally as long as 180 feet.

Its breadth of "fifty cubits," or 75 feet, is much greater than is ever found in Assyria. This difference indicates that the two cultures employed very different methods of roofing. The use of pillars allowed the Jews, like the Persians, to cover a very wide space.

Regarding the "four rows" of pillars, the Septuagint specifies "three rows." If there were forty-five pillars as mentioned in 1 Kings 7:3, arranged with fifteen in each row, there would have been only three rows. This arrangement seems to match the old palace of Cyrus at Pasargadae. If there were four rows of fifteen pillars, the total number would have been sixty.