You must not add to or subtract from what I command you, so that you may keep the commandments of the LORD your God that I am giving you.
KJV
Ye shall not add unto the word which I command you, neither shall ye diminish [ought] from it, that ye may keep the commandments of the LORD your God which I command you.
ASV
Ye shall not add unto the word which I command you, neither shall ye diminish from it, that ye may keep the commandments of Jehovah your God which I command you.