Musar zu Dewarim 7:18

לא תירא מהם…כי תאמר בלבבך רבים הגוים האלה . I have written a commentary on this verse (7,17) elsewhere in which the word כי is treated as פשט, and divergent from the forced explanation of Rashi who comes to the conclusion that the word must be translated as "perhaps, maybe." I believe the meaning is: "If you say in your heart that you could never conquer these nations in the normal way without the active assistance by G–d because they are too numerous, I, G–d, tell you not to fear them because I will certainly assist you." If, on the other hand, you imagine that you are capable of accomplishing this task with your own strength, then you have reason to be afraid." The Torah spells this out later on in 8,12-18, etc., where Israel is warned not to ascribe its success to its own might.