Joshua 6:8-10

8And just as Joshua had commanded the people, the seven priests bearing the seven trumpets of rams' horns before the Lord went forward, blowing the trumpets, with the ark of the covenant of the Lord following them.

9The armed men were walking before the priests who were blowing the trumpets, and the rear guard was walking after the ark, while the trumpets blew continually.

10But Joshua commanded the people, "You shall not shout or make your voice heard, neither shall any word go out of your mouth, until the day I tell you to shout. Then you shall shout."