And Joshua set up twelve stones in the midst of the Jordan, in the place where the feet of the priests bearing the ark of the covenant had stood; and they are there to this day.
9. And Joshua set up twelve stones, etc Apparently there was no use of stones under the water, and it may therefore seem to have been absurd to bury stones at a depth. The others which were placed in Gilgal being publicly visible, furnished occasion for inquiry; but stones hidden from the eyes of men at the bottom of the water could have no effect in inciting their minds.
Joshua had his hands full moving wives, children, cattle, tents, and all their effects across a treacherous ford while an enemy watched; yet even in that press of business, he would not delay the memorial God required. Mark this: however urgent our own affairs, we dare not neglect what belongs to God's glory and His honour, for that is our truest business.
AI summary
Commenting on Joshua 4:1-9
And Joshua set up twelve stones in the midst of Jordan,.... Twelve other stones, as the Septuagint and Vulgate Latin versions, and so Jarchi; which he set one upon another, so that they might be seen above the water; or however the water of Jordan being clear, they might easily be discerned by those who either passed over the river, or walked by the side...