Joash said to all who stood against him, Will you contend for Baal? Or will you save him? he who will contend for him, let him be put to death while [it is yet] morning: if he be a god, let him contend for himself, because one has broken down his altar.
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.