“when the priests...had come up out of the midst of the Jordan.” The exact timing of the priests leaving the Jordan River and the water returning at that same time is more evidence that this is a great miracle of Yahweh and that He is able to control things that happen on earth. The gods of the Canaanites could not do that. Also, this verse gives evidence that “midst” does not always mean “middle,” but just somewhere “in” something, in this case, the ark was close to the edge of the Jordan, not in the middle.
“separated from the ground.” When the feet of the priests stepped off the dry riverbed of the Jordan River, Yahweh let the water flow back down the riverbed and over the banks as it had been flowing before. The riverbed had been made “dry” by God, so the verse is not primarily saying that when the feet of the priests stepped “onto” the dry ground, but rather when the priest’s feet “separated from” the dry ground of the riverbed that the water returned. In Joshua 3:17 the feet of the priests stood firm on the dry ground, and here the feet of the priests are separated from that dry ground and the water then returned. The HALOTa gets the sense of the separation of the priest’s feet from the riverbed correct because it says, “be raised from the ground,” that is, the feet of the priests were “raised from the ground” of the riverbed, not “set down” on the bank of the Jordan River.
“the Jordan returned.” The Hebrew verb “returned” is the same as when Yahweh held back the waters of the Red Sea and then the sea “returned” upon the Egyptian army (Exod. 14:26, 28). It is clear in both the Exodus record and here in Joshua that it is Yahweh who has the power to split the sea and stop the river.