So they ask Him at the start of Judges-who should go in there and take care of the Canaanites. God sends Judah first. Judah in heaven, wars in worship. The part of God which is mighty swift judging and teaching simultaneously. So then going back to the start of Joshua which is sort of the map for now-the levites go in first-Presence preceeds possession, then the judah folks get their back-the general Body is a ways back and not to move til they see the ark go.
To get to the exact moment we are at-the priest feet-the soles of their feet–the sole of foot speaks of vulnerability..these are the ones being asked to step out and stand still on the edge of the Jordan, just carrying the Presence, and allowing it to part the waters. They are vulnerable because the general Body cannot see what they are doing, and they are the first ones to the Jordan. But God says stand still, and I will part the waters-and then in that verse, I will do so as a sign for those who are behind you that I will “push back” the enemy in the land promised (so God is teaching again). But the exact moment is this edge of the Jordan place, and God is sort of like-these guys need to know who they are so they can start taking their place here on the banks of the harvesting river!!!