John Calvin Commentary Joshua 4:16

"Command the priests that bear the ark of the testimony, that they come up out of the Jordan." — Joshua 4:16 (ASV)

Command the priests, etc. Here it is shown more clearly how meekly and calmly the priests yielded implicit obedience to the divine command, for they did not move a foot until Joshua ordered the signal to retire. But as it was an instance of rare virtue to be thus modest and obedient, so the fatherly kindness of God is conspicuous in this, that he condescended to direct and govern almost every step in their progress by his own voice, lest any perplexity might occur to hinder them.

Next follows a more conspicuous confirmation of the miracle; for as soon as they climbed the opposite bank, the Jordan began again to flow as usual. If it had not returned to its former state, and indeed, suddenly, many would have imagined the cause of the change to be hidden but accidental. But when God displays his power and favor at such brief and distinct intervals, all doubt is removed. The moment the feet of the priests were made wet, the Jordan retired; now on their departure, it recovers its free course, and that at the very instant when they reached the bank. For the term dry here means that part which was not covered by the overflow. Thus the river, though mute, was the best of heralds, proclaiming with a loud voice that heaven and earth are subject to the God of Israel.