The old spiritual is based on Joshua 5:13–27. Joshua, leader of the Israelite after Moses died, was told by an angel how to capture the strongly fortified city of Jericho.
Instead of attacking, the Israelites were to march around the city for six days, carrying the ark of the covenant. On the seventh day, priests were to blow trumpets and the people were to shout.
When they did this, the city walls fell (as the song says, “and de walls come tumblin’ down”), and the Israelites captured the city.