What do we learn from this verse?
Malbim: David had already prepared enough cedar trees for the Beis ha'Mikdash in the Levanon in Eretz Yisrael, and enough [converts] to quarry stones from the mountain and to carry them, like it says above (Divrei ha'Yamim 1, Perek 22 1 ). Shlomo needed more trees and workers 2 only because he wanted to build also a royal house.
It says there (verse 14) that David told Shlomo to add to what David prepared! Malbim must explain that he said to add in order to build also a royal house. The verses here say that Shlomo asked Chiram to help him to build Beis Hashem; Malbim explains that he hinted also to a royal house. I do not know what forced him to explain so. (PF)
Sanhedrin 104b: A Bas Kol said "Ish Mahir bi'Mlachto?" - Shlomo built the Mikdash before his house, and rushed to build it quicker. (in seven years) than his house (in 13 years. Surely Shlomo finished Beis Hashem before starting his house. If he used more workers for his house than for the Mikdash, why is he praised for being more zealous to build the Mikdash than his own house?! And why did he ask for more workers now, if he will not need them until years from now? (PF)


