John Gill 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 a copy of the law of
Moses
Not upon the stones of which the altar was made, though some have so thought; but upon other stones erected in the form of a pillar, and plastered over, (Deuteronomy 27:4) ; which copy of the law was not the whole book of Deuteronomy, as some, at least only an abstract of the laws in it; but rather the decalogue, as Abarbinel; or the blessings and curses later read, as Ben Gersom:

which he wrote in the presence of the children of Israel :
they being witness of it, that he did what was enjoined.