Because of his strength will I wait upon thee - literally, “His strength - I will wait upon thee.” The reference here is not to the strength or power of God, as if the fact that “He” was powerful was a reason why the psalmist should look to him - but it is to the strength or power of the enemy - of Saul and his followers. There is much abruptness in the expression. The psalmist looks at the power of his enemy. “‘His strength,’ he cries. It is great. It is beyond my power to resist it. It is so great that I have no other refuge but God; and because it is so great, I will fix my eyes on him alone.” The word rendered “wait upon” means rather to look to; to observe; to fix the eyes upon.
For God is my defense - Margin, “My high place.” That is, God was to him “as” a high place, or a place of refuge; a place where he would be safe. See the notes at Psalms 18:2.