Joshua 6:10

‘ And Joshua had commanded the people saying, “You shall not shout, nor let your voice be heard, neither shall any word proceed out of your mouth, until the day I bid you shout, then shall you shout.” '

The people were ordered not to make any sound while they marched. They were to march in total silence, without shouting, without talking, without a murmur. There was to be total silence, until Joshua gave the order and then they were to shout loudly. This would have an unnerving effect on the watchers who would have expected taunts and battlecries. The latter would have enabled them to shout back and build up their own resistance, but shouting at a silent enemy was a waste of energy. The silence stressed the presence of YHWH among them. In His presence none dared speak (Habakkuk 2:20). It also demonstrated that the result was the work of YHWH (Exodus 14:14). Their shout would declare His triumph (Psalms 47:1).