Gideon said to God, Don't let your anger be kindled against me, and I will speak but this once: Please let me make a trial just this once with the fleece; let it now be dry only on the fleece, and on all the ground let there be dew.
Perhaps Gideon used a woolen fleece simply because it was handy. He asked God to cause the dew to settle on the fleece that night but not on the surrounding ground. In the morning he discovered that is what God had done. Gideon may have concluded that he had asked the wrong thing since wool attracts dew. In any case he asked God to let the dew fall on the ground but not on the fleece the next night. God did this too. Thus, this double demonstration, that God was indeed with him, and would grant him victory as He had promised, strengthened Gideon’s faith.