John Calvin Commentary Joshua 8:32

"And he wrote there upon the stones a copy of the law of Moses, which he wrote, in the presence of the children of Israel." — Joshua 8:32 (ASV)

And he wrote there upon the stones, etc. A different rule applies to the stones mentioned here, on which God wished that a memorial of his Law should always appear, so that a kind of barrier might be placed to protect pure religion against the superstitions of Egypt.

They were therefore covered with lime, so that they might be more conspicuous and the writing on them more distinct. I willingly subscribe to the opinion of those who understand by the repeated Law a written form, or what is commonly called a copy or duplicate. I cannot, however, believe that the whole volume was traced on them, because no stones, however large, could suffice to contain all the details. I therefore think that by the term Law, only its substance and sanctions are denoted.

This made it palpable, even to strangers entering the land, what God was worshipped in it, and all excuse for error was taken away, when the Law was not stored away in a book but was made manifest to the eyes of all. In short, even if the priests had been silent, the stones themselves spoke clearly.