וַיִּבֶן֩ אֶת־קִיר֨וֹת הַבַּ֤יִת מִבַּ֙יְתָה֙ בְּצַלְע֣וֹת אֲרָזִ֔ים מִקַּרְקַ֤ע הַבַּ֙יִת֙ עַד־קִיר֣וֹת הַסִּפֻּ֔ן צִפָּ֥ה עֵ֖ץ מִבָּ֑יִת וַיְצַ֛ף אֶת־קַרְקַ֥ע הַבַּ֖יִת בְּצַלְע֥וֹת בְּרוֹשִֽׁים׃
And he built the walls of the house within with boards of cedar; from the floor of the house unto the joists of the ceiling, he covered them on the inside with wood; and he covered the floor of the house with boards of cypress.
Read kabbalistic (mystical) interpretation of I Kings 6:15: and classical mystical sources.