For they came up with their cattle and their tents; they came in as locusts for multitude; both they and their camels were without number: and they came into the land to destroy it.
So here was Gideon hiding from the Midianites as he was threshing the wheat because if the Midianites had caught him they'd take the wheat. And so he was out by the winepress threshing wheat and here was an angel sitting under an oak tree.