Matthew Poole and continuators on Joshua 4:9

9 And Joshua set up twelve stones in the midst of Jordan , in the place where the feet of the priests, which bare the ark of the covenant, stood: and they are there unto this day .

Properly so called, as Iosh. 3. 17. Qu. How could these stones be a Monument of this work, when they were not seen, but generally covered with the Waters of Iordan? Ans. These stones are not the same with those which a man could carry upon his shoulders, v. 5. And therefore might be very much larger; and being set up in two rows one above another, they might possibly be seen, at least some times when the Water was low, and especially where the Water was commonly more shallow, as it might be ordinarily in this place, though not at this time when Iordan overflowed all its banks. Add to this, That the Waters of Iordan are said to be very pure and clear; and therefore these stones, though they did not appear above it, might be seen in it, either by those who stood upon the shore, because that River was not broad; or at least by those that passed in Boats upon the River, who could easily discern them by the peculiar noise and motion of the Water occasioned by that heap of stones. And this was sufficient, especially considering that there was another more distinct and visible Monument of this Miracle set up in Gilgal.

This might be written either, 1. by Ioshua who wrote this Book near 20. years after this was done: Or, 2. by some other holy man divinely inspired and approved of by the whole Iewish Church, who inserted this and some such passages both in this Book, and in the Writings of Moses.