Charles Ellicott Commentary Deuteronomy 12:32

"What thing soever I command you, that shall ye observe to do: thou shalt not add thereto, nor diminish from it." — Deuteronomy 12:32 (ASV)

What thing soever I command you. — No later writer could put these words into the mouth of Moses, if he had altered the precepts of Moses to any appreciable extent.