(To prove that he was really God. God passed the this test, too, by the way. No sweat.)
To keep a fleece dry while making the ground wet
And Gideon said unto God, Let not thine anger be hot against me, and I will speak but this once: let me prove, I pray thee,
but this once with the fleece; let it now be dry only upon the fleece, and upon all the ground let there be dew.