Midrasz do Jozuego 4:18

As soon as the last man of Israel ascended from the Jordan, the water of the Jordan returned to its place, as it is said (Josh. 4, 18) And it came to pass, when the priests that bore the ark of the covenant of the Lord came up out of the midst of the Jordan as soon as the soles of the priest's feet were drawn up unto the dry ground, that the waters of the Jordan returned unto their place, and flowed over all its banks, as aforetime. It is thus found that the ark and the priest, its bearer, was on one side of the Jordan and Israel was on the other side of the Jordan, hence the ark carried its own bearers and crossed the Jordan, as it is said (Ib., ib. 11) And it came to pass, when all the people had finished passing over the Jordan, that the ark of the Lord passed over it with the priests in the presence of the people. Concerning this it happened that Uzzah was punished, as it is said (II Sam. 6, 6) And when they came to the threshing floor of Nachon, Uzzah put forth his hand to the ark of God and took hold of it; for the oxen shook it. Thereupon the Holy One, praised be He, said unto Uzzah: "The Holy Ark carries its own bearers, how much the more could it carry itself!" Therefore (Ib., ib. 7)