Charles Ellicott Commentary Exodus 18:11

"Now I know that Jehovah is greater than all gods; yea, in the thing wherein they dealt proudly against them." — Exodus 18:11 (ASV)

For in the thing ... — Hebrew, even in the matter in which they dealt proudly against them. Jehovah’s superior power had been shown especially in the matter in which the Egyptians had dealt most proudly—namely, in pursuing the Israelites with an army when they had given them leave to depart, and attempting to re-capture or destroy them.