John Calvin Commentary Joshua 6:15

"And it came to pass on the seventh day, that they rose early at the dawning of the day, and compassed the city after the same manner seven times: only on the day they compassed the city seven times." — Joshua 6:15 (ASV)

And it came to pass on the seventh day, etc. Here, too, by leading the people around the city so often, God seemed not only to keep the matter in suspense but also purposely to toy with the miseries of the people, who were exhausting themselves to no avail. For why does he not order them suddenly to attack the city?

Why does he keep them in their continued silence, even until they were weary, and not allow them to open their mouths to shout? But the blessed result of this endurance teaches us, that there is nothing better than to leave the decisive moments and opportunities for action at his disposal. We should not, through our haste, try to anticipate his providence, for if we do not submit to it, we obstruct the course of his agency.

Therefore, while the priests were sounding their horns, God ordered a corresponding shout to be raised by the people. In this way, he could demonstrate that he is not pleased with any impulsiveness that people display on their own initiative. Instead, he above all things requires a disciplined zeal, the only rule of which is not to move tongue, foot, or hand until he orders. Here, the rams’ horns undoubtedly represented his authority.