The home of the Israelites' that God gave them had been taken over by the Midianites. God wanted them to get their land back and live in peace. He choose Gideon to lead the Israelites to reclaim their land.
One day God spoke to Gideon while he was hiding so that the Midianites would not see him. He was thrashing wheat by hand in a bottom of a pit where grapes were pressed to make wine. The Angel of the Lord said "You are a Mighty man of Valour, and the Lord is with you."
Gideon replied. "If the Lord is with us, why has all this bad happen to us? And where are all the miracles that our ancestors have told us about - such as when God brought them out of Egypt?" Now the Lord has thrown us away and has let the Midianites completely ruin us."
Then the Lord turned to him and said. "I will make you strong! Go and save Israel from the Midianites! I am sending you."
But Gideon replied, "Sir, how can I save Israel? My family is the poorest in the whole tribe of Manasseh, and I am the least thought of in the entire family!"
Whereupon the Lord said to him, "But I, Jehovah, will be with you! And you shall quickly destroy the Midianite hordes!"
Gideon replied, "If it is really true that you are going to help me like that, then do some miracle to prove it! Prove that it is really Jehovah who is talking to me! But stay here until I go and get a present for you." "All right," the Angel agreed. "I'll stay here until you return."
Gideon hurried home and roasted a young goat, and baked some unleavened bread from a bushel of flour. Then, carrying the meat in a basket and broth in a pot, he took it out to the Angel, who was beneath the oak tree, and presented it to him. The Angel said to him. "Place the meat and the bread upon that rock over there, and pour the broth over it." When Gideon had followed these instructions, the Angel touched the meat and bread with his staff, and fire flamed up from the rock and consumed them! And suddenly the Angel was gone! When Gideon realized that it had indeed been the Angel of the Lord he cried out, "Alas, O Lord God, for I have seen the Angel of the Lord face to face!"
"It's all right," the Lord replied. "Don't be afraid! You shall not die." And Gideon built an altar there and named it "The Altar of Peace with Jehovah."
Judges 6: 11-24 The Living Bible
Gideon had to be sure God was speaking to him. So he put a fleece of wool outside, then he said "Tomorrow if there is dew on the fleece only, and it is dry on all the ground, then I shall know that you God will save Israel by my hand, as God has said."