Gideon, who had been chosen by God to lead Israel’s armies, wanted a sign that God really was with him.
He laid out a fleece on the ground and told God to give him a sign: If, the next morning, the fleece was wet and the ground around it dry, he would believe. God did so, and Gideon wrung out a bowlful of water from the fleece.
Then he asked God to do the opposite: At night, leave the fleece dry but make the ground wet with dew. God did, and Gideon believed.
(See Judg. 6:36–40.) The expression “laying out the fleece” refers to this kind of testing of someone.