What are "Tzal'os Arazim"?
Gra: They are thin cedar planks, which are good for covering.
What is "Ad Kiros ha'Sipun"?
Rashi: It is [until the walls of] the Aliyah.
Radak citing Targum Yonasan: It is until the ends of the beams near the ceiling.
Why did he cover the walls with cedar wood?
Rashi: He wanted to cover it with gold (verse 21). Gold will not stick to rocks, but it can be stuck to wood via nails.
Radak: It was so the rocks will be seen (verse 18).
What is "Es Karka ha'Bayis"?
Rashi: It is the entire floor.
Why did he cover the walls with cedar wood, and the floor with Beroshim?
Gra: Cedars are tall, so he used them for the walls. Beroshim are not so tall, but they are wider, so they are good for the floor. "Koros Bateinu Arazim Rehitenu Berosim" (Shir ha'Shirim 1:17) - Rehitenu, the floor on which they walk, is of Beroshim.
Why does it say in Divrei ha'Yamim II, 3:5 that he covered the Bayis ha'Gadol with Beroshim?
