Joshua 4:1-3 - Choose twelve men

4:1

We now come to the actual crossing, this is a very undramatic affair compared with the crossing of the Red Sea, largely because of the absence of any pursuing enemy. The battles will come once they have crossed.

4:2,3

There is no doubt that they will successfully cross the Jordan. Instead the focus is on setting up memorial stones. One man is to be chosen from each of the twelve tribes. Each of these is to take up a stone from the middle of the Jordan, where the priests were standing. The stones were presumably of a reasonable size, and they were to be taken from the middle so that it was beyond doubt that they had not just been taken from the edge. They were a proof and reminder of what had happened.