Albert Barnes Commentary 2 Chronicles 3:8

"And he made the most holy house: the length thereof, according to the breadth of the house, was twenty cubits, and the breadth thereof twenty cubits; and he overlaid it with fine gold, amounting to six hundred talents." — 2 Chronicles 3:8 (ASV)

The most holy house - that is, the sanctuary, or holy of holies. On the probable value of the gold, see the note on 1 Kings 10:14.