1)
Why did he say "Rumah Hashem b'Uzecha"?
1.
Rashi: [Rise with Your strength against those who stand against You], and we will sing [about Your Gevurah]!
2.
Radak: All Yisrael will say, rise against the enemies with Your Gevurah, for strength is to You, and not to us!
3.
Malbim: He began with "b'Azecha Yismach Melech" (verse 2). Therefore he requests that Hashem rise with His strength.
2)
Why did he say "Nashirah u'Nezamrah Gevurasecha"?
1.
Radak: With the strength that You give to us, we will sing to and thank You, for everything is from You.
2.
Malbim: Take vengeance against the Goyim, and we will sing about Your Gevurah.
