Charles Ellicott Commentary Judges 7:5

"So he brought down the people unto the water: and Jehovah said unto Gideon, Every one that lappeth of the water with his tongue, as a dog lappeth, him shalt thou set by himself; likewise every one that boweth down upon his knees to drink." — Judges 7:5 (ASV)

Every one that lappeth of the water with his tongue. —Josephus (Antt. v. 6, § 4) says that Gideon led them down to the spring in the fiercest heat of the noonday, and that he judged those to be the bravest who flung themselves down and drank, and those to be the cowards who lapped the water hastily and tumultuously. Theodoret also thinks that the Divine aid was shown by the fact that the greatest cowards were chosen.

This may have been a Jewish legend (Hagadah); but it seems more reasonable to suppose that greater self-control would be shown by stooping and drinking the water out of the hand than by flinging themselves at full length to drink, which would be the natural instinct of a thirsty man. Rashi says that those who went down on their knees to drink were secret idolators, who had bowed the knee to Baal (1 Kings 19:18).

As a dog lappeth. —Some commentators imagine that this is an allusion to Egyptian dogs, who, out of fear for the Nile crocodiles, only venture to lap the water while they are running along the banks.