Charles Ellicott Commentary Judges 6:37

"behold, I will put a fleece of wool on the threshing-floor; if there be dew on the fleece only, and it be dry upon all the ground, then shall I know that thou wilt save Israel by my hand, as thou hast spoken." — Judges 6:37 (ASV)

A fleece of wool. — In works of art this is sometimes represented as an entire sheepskin, probably from an erroneous explanation of the Vulgate, Vellus lanae, and from Luther’s rendering, ein Fell mit der Wolle. But the English version is correct.

In the floor. — That is, on the open threshing-floor. (See Note on Judges 6:11, and compare to Psalms 1:4; Hosea 13:3.)

If the dew is on the fleece only. — The very fact that this circumstance might be a purely natural result only shows the simple truthfulness of the narrative. Gideon would hardly have asked for this sign if he had been aware that, taken alone, it would be no sign of supernatural guidance. Bishop Hervey quotes Lord Bacon, who says (Nat. Hist.) that “Sailors have used every night to hang fleeces of wool on the sides of their ships towards the water, and they have crushed fresh water out of them in the morning.” Every one must have noticed flocks of wool on the hedges, sparkling with dewdrops long after the dew on the leaves around them has evaporated.

In Psalms 72:6 (Prayer Book), the verse He shall come down like the rain into a fleece of wool, uses the same Hebrew word as in this passage. The ancient versions also understand it in the same sense (Septuagint, epi plokon; Vulgate, in vellus). However, perhaps the true meaning there is “mown grass,” as in Amos 7:1 (mowings).