1)
Why did he say "v'Atah Tenah Li?"?
1.
Malbim: Hashem sustained me and my strength, so I can dispossess them.
2)
What is the meaning of "Hashem Osi"?
1.
Radak, Metzudas Tziyon: It is as if said Imi (with me). We find like this - "va'Adaber Osach" (Yechezkel 2:1).
2.
Malbim: It should have said Iti (with me). This is like "va'Shem Osi k'Gibor Aritz" (Yirmeyah 20:11) - he is my Os (sign), or strength.
