Judges - Chapter 6
Midian and Gideon
After 40 years of peace, the nation once again slacked off and G-d allowed Midian to occupy the country. The Midianites were particularly cruel; they didn't just raid the Jews' crops, they destroyed what they couldn't use. (Verse 5 compares them to a swarm of locusts.) The people cried out and G-d sent Gideon (Gidon in Hebrew, but we'll stick with the English).
Gideon was threshing wheat at his winepress in an effort to conceal it from the Midianites when G-d sent an angel to give him his "marching orders." Considering himself unworthy, Gideon asked for a sign. The angel had him put meat, matzos and broth on a rock. (The broth was poured over the solid food.) A fire came out of the rock and consumed the offering. (Yes, this is a preview of the miracle later wrought for Elijah in the Book of Kings.)
That night, G-d had Gideon break apart his father's altar to the Baal and cut down his Asheira (a tree worshipped for idolatry). He built an altar to Hashem and sacrificed his father's fattened bull on it, using the wood of the Asheira for kindling. The next morning, when the people of the town learned what Gideon had done, they wanted to kill him. Gideon's father Yoash interceded, saying that if Baal has a problem with what Gideon did, and if Baal had the ability to deal with it, then Baal would deal with it himself. This earned Gideon the nickname "Yerubaal," "let the Baal handle it."
Finally, Gideon asked for a sign so that the people would know he was sent by G-d. Gideon laid out a fleece on the threshing floor. On one night, the dew fell only on the fleece, not on the ground. On the next, the dew fell only on the ground, not on the fleece.