שְׁלֹ֧שֶׁת אֲלָפִ֛ים כִּכְּרֵ֥י זָהָ֖ב מִזְּהַ֣ב אוֹפִ֑יר וְשִׁבְעַ֨ת אֲלָפִ֤ים כִּכַּר־כֶּ֙סֶף֙ מְזֻקָּ֔ק לָט֖וּחַ קִיר֥וֹת הַבָּתִּֽים׃
even three thousand talents of gold, of the gold of Ophir, and seven thousand talents of refined silver, wherewith to overlay the walls of the houses;
Rashi on I Chronicles
to overlay the walls of the houses and no one can overlay anything, either with silver or with gold, unless it is refined.