John Gill Commentary 1 Kings 7:3

"And it was covered with cedar above over the forty and five beams, that were upon the pillars; fifteen in a row." — 1 Kings 7:3 (ASV)

And it was covered with cedar above the beams, that lay on
forty five pillars, fifteen in a row. On the second floor were three rows of pillars, fifteen in a row, which made forty five, that stood to east, north, and south; and upon these pillars beams, which were the floor of the third story, over which was a roof of cedar wood.