John Calvin Commentary Joshua 3:11

"Behold, the ark of the covenant of the Lord of all the earth passeth over before you into the Jordan." — Joshua 3:11 (ASV)

Behold the ark of the covenant, etc. First, he says that the ark of God will go before; and secondly, he explains for what purpose: namely, that the Jordan may withdraw from its place, trembling, so to speak, at the presence of the Lord, as is said in the Psalms (Psalms 114). The narrative introduced concerning the twelve men is parenthetical, as it only briefly alludes to what it will afterwards deliver more fully and clearly. At present, let us merely understand that while the ark went before, God displayed his power in guiding the people. And in this way, there was a confirmation of the sanctity of the worship appointed by the Law, when the Israelites perceived that it was no empty symbol of his presence that God had deposited with them. For the Jordan was compelled to yield obedience to God just as if it had beheld his majesty.

Let us, however, remember that the only reason which induced the Lord to display his grace in the ark was because he had placed the tables of his covenant within it. Moreover, as this could not be easily believed, Joshua directs the mind of the people to the contemplation of the divine power, which surmounts all difficulties. The title 'Ruler of the whole earth,' here applied to God, is not insignificant but rather extols his power above all the elements of nature, so that the Israelites, considering how seas and rivers are subject to his dominion, might have no doubt that the waters, though naturally liquid, would become stable in obedience to his word.