1)
What is the meaning of "u'Mi Ya'atzor Ko'ach"?
1.
'Rashi': Do not think that I build a big building proper for Hashem. No one can build a building proper for Him! This is like "Ki Natzor Ko'ach Lehisnadev" (Divrei ha'Yamim I, 29:14).
2)
Why did he say that Shamayim cannot contain Hashem?
1.
'Rashi': I do not build a building proper for Him. It is merely needed to burn [Ketores and Korbanos] in front of Him.
2.
Malbim: If the Bayis were to dwell in it, a royal house would suffice. However, this is not possible. The Bayis is only for His honor; therefore, its honor must be according to the honor of the One for whose honor it is built.
