John Calvin Commentary Joshua 4:10

"For the priests that bare the ark stood in the midst of the Jordan, until everything was finished that Jehovah commanded Joshua to speak unto the people, according to all that Moses commanded Joshua: and the people hasted and passed over." — Joshua 4:10 (ASV)

For the priests which bare, etc. If we are ordered to halt while others are hurrying, we know how easily a feeling of annoyance is produced, because we seem to be occupying an inferior position. The priests, therefore, are justly praised for their patience in calmly remaining alone at their post, while the whole people were swiftly hurrying on to the opposite bank. For they might have begun to feel doubtful, fearing that the heaps of water suspended over their heads might suddenly melt away and engulf them. They therefore demonstrated their piety as much by remaining there as by venturing to go into the opposing current.

Thus, in the first place, they displayed their ready obedience, and in the second, their constancy, making it clear that they had not obeyed from impulse alone. For their steadfastness, which is praised, must have originated from a living principle. It was a proof of modesty that they attempted nothing rashly, but regulated their whole procedure, as it were, in strict conformity to the word of God.

Although it is probable that Joshua was instructed by a new message from heaven about what needed to be done, he is, however, said to have followed what Moses had commanded. By this, I understand that Moses had carefully instructed him to depend on God's every word. Joshua was thoroughly obedient to this instruction and, accordingly, was always attentive to what pleased God. In short, the command of Moses mentioned here was general, but God gave specific instructions to Joshua as each situation arose.