When you hear the signal from the ram’s horn, ¹  have the whole army give a loud battle cry. ²  Then the city wall will collapse ³  and the warriors should charge straight ahead.” ⁴ 

Have seven priests carry seven rams’ horns ¹  in front of the ark. On the seventh day march around the city seven times, while the priests blow the horns.

So Joshua son of Nun summoned the priests and instructed them, “Pick up the ark of the covenant, and seven priests must carry seven rams’ horns in front of the ark of the Lord.”