Commentary for Joshua 6:3

So you shall do for six days: Don't ask the reason for the decision of the Creator why there was need for this encircling, and the reason for the 7 priests, the 7 shofars, the 7 circles, and the 7 days. The reason for the circle with the teruah-blast is to separate the people that were in the city and the wall will fall under it, "So that all the nations of the land will know that Hashem is fighting for Israel, not with sword or spear..." The number 7 has great meaning in science - like the 7 altars and the 7 sacrificial cows. And 7 is also the chosen number for counting days and for the natural world.