And it came to pass, when the priests that bore the ark of the covenant of the LORD were come up out of the midst of Jordan, and the soles of the priests' feet were lifted up unto the dry land, that the waters of Jordan returned unto their place, and flowed over all its banks, as they did before.
Read Chapter 4
Procopius of Gaza
After they had crossed over the Jordan, the waters returned to their place and overflowed all its banks as before. For the mystical Jordan also increases when the full number of the faithful enters in. Accordingly, we read, “Lift up your eyes and see that the fields are ripe for the harvest,” and again, “The harvest is plentiful but the laborers are few.” But he does not simply say “harvest” but “wheat,” according to what they have in the Septuagint. For this is a symbol of nourishment. - "Commentary on Joshua 4.18"