And we journeyed from Chorev and we went through all that great and fearful desert.": They saw snakes as (large as) the beams of the olive press and scorpions as large as bows stretched out before them. Now does this not follow a fortiori, viz.: If I have subdued before them such unnatural things, how much more so, things which are within the province of nature, (like the seven nations)! Thus, "And we journeyed from Chorev, etc."
(Devarim 1:20) "And I said to you … as the L-rd … has spoken, etc.": Moses said to them: It is not of myself that I speak thus to you, but at the behest of the Holy One Blessed be He.