Shofetim 6:36-40

And Gid'on said unto HaElohim, If Thou wilt save Yisroel by my yad, as Thou hast said, Hinei, I will put a fleece of wool in the goren (threshing floor); and if the tal (dew) be on the fleece only, and it be dry upon all ha'aretz, then shall I know that Thou wilt save Yisroel by my yad, as Thou hast said. And it was so; for he rose up early on the next day, and squeezed the fleece together, and wrung the tal out of the fleece, a bowl full of mayim. And Gid'on said unto HaElohim, Let not Thine anger be hot against me, and I will speak but this once; let me test, now, but this once with the fleece; let it now be dry only upon the fleece, and upon all the ground let there be tal. And Elohim did so that night; for it was dry upon the fleece only, and there was tal on all the ground.