Deuteronomy 4:2-3

2Ye shall not add to the word which I command you, neither shall ye take from it, that ye may keep the commandments of Jehovah your 1God which I command you.

3Your eyes have seen what Jehovah did because of Baal-Peor; for all the men that followed Baal-Peor, Jehovah thy 2God hath destroyed them from among you;