Joshua 4:9 - Wesley's Explanatory Notes

Twelve stones — These stones are not the same with those which a man could carry upon his shoulder, Joshua 4:5. They might be very much larger; and being set up in two rows one above another, might be seen, at least when the water was low, especially where it was shallow, as it was ordinarily, though not at this time, when Jordan overflowed all its banks. Add to this, that the waters of Jordan are very clear; therefore these stones might be seen in it, either by those who stood upon the shore, because the river was not broad; or by those that passed in boats. Unto this day — This might be written, either by Joshua who probably wrote this book near 20 years after this was done: or, by some other holy man divinely inspired, who inserted this and some such passages both in this book and in the writings of Moses.