1)
Why did he say "Kumah Elokim"?
1.
Radak: If You will not do for us, do for Yourself!
2)
Why did he say "Rivah Rivecha"?
1.
Radak: Our feud is Your feud, for the enemy blasphemed You, and said that You lack ability to take us out from them.
2.
Malbim: You should fight Your battle due to Your profaned name.
3)
What is "Cherpasecha"?
1.
Rashi: Their blasphemy of You - 'Zos Oyev Cheref" (verse 18).
4)
Why does it say "Mini Naval Kol ha'Yom"?
1.
Malbim: [Other reasons to fight Your battle are] (a) the lowliness of the reviler (Naval, this magnifies the shame); (b) the blasphemy is constant; (c) they mock You (verse 23).
