Jamieson, Fausset and Brown on Judges 7:13

13. I dreamed a dream, and, lo, a cake of barley bread tumbled into the host of Midian--This was a characteristic and very expressive dream for an Arab in the circumstances. The rolling down the hill, striking against the tents, and overturning them, naturally enough connected it in his mind with the position and meditated attack of the Israelitish leader. The circumstance of the cake, too, was very significant. Barley was usually the food of the poor, and of beasts; but most probably, from the widespread destruction of the crops by the invaders, multitudes must have been reduced to poor and scanty fare.