Ye shall not shout; because shouting before the time appointed would be ineffectual, and so might give them some discouragement, and their enemies matter of insulting.
Related Commentaries of Joshua 6:10
Joshua 6:10
10 And Joshua had commanded the people, saying, Ye shall not shout, nor make any noisec with your voice, neither shall any word proceed out of your mouth, until the day I bid you shout; then shall ye shout.