and they encamped against them, and destroyed the increase of the earth, until you come to Gaza, and left no sustenance in Israel, neither sheep, nor ox, nor donkey.
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.