Joshua 6:8-10

8And it was so, that when Joshua had spoken to the people, the seven priests carrying the seven trumpets made of rams’ horns went on before the Lord and blew the trumpets; then the ark of the covenant of the Lord went behind them.

9The armed men went in front of the priests who blew the trumpets, and the rear guard came after the ark, while the priests continued to blow the trumpets.

10But Joshua commanded the people, “You shall not shout [the battle cry] nor let your voice be heard nor let a word come out of your mouth, until the day I tell you to shout. Then you shall shout!”