Judges 7:16-18

16And he divided the three hundred men into three companies, and he put a trumpet in every man's hand, and empty pitchers, and torches within the pitchers.

17And he said to them, Look on me, and do likewise; behold, when I come to the extremity of the camp, it shall be that, as I do, so shall ye do.

18And when I blow with a trumpet, I and all that are with me, ye also shall blow the trumpets around the whole camp, and shall say, For Jehovah and for Gideon!