Joshua 4:18
And it came to pass, when the priests that bare 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 his banks, as they did before.
When the priests bearing the ark of the covenant came up out of the midst of the Jordan and the soles of their feet were lifted onto dry land, the waters of the Jordan returned to their place and flowed over all its banks as before. They reached the western shore, and as soon as their feet left the riverbed the river suddenly resumed its natural course after the miraculous crossing. The river at that time was swollen and impetuous, making the sudden return to its channel all the more striking.
God Himself held the river back until Israel had fully crossed, and when He removed His power and mighty hand the water rushed back down its course. The return of the river in this manner confirmed that the crossing had been miraculous and strengthened Israel's faith.
The stones taken from the riverbed and set up beyond the Jordan were a lasting witness to this deliverance, so that later generations would hear how powerfully God had acted and would fear Him forever. The return of the waters marks the end of Israel's passage across the Jordan into the promised land, an experience whose lessons were to be remembered and studied.