Deuteronomy 4:2

4:2 Do not add a thing to what I command you nor subtract from it, so that you may keep the commandments of the Lord your God that I am delivering to you.

Deuteronomy 12:32--13:11

Idolatry and False Prophets

12:32 (13:1) You must be careful to do everything I am commanding you. Do not add to it or subtract from it! 13:1 Suppose a prophet or one who foretells by dreams should appear among you and show you a sign or wonder, 13:2 and the sign or wonder should come to pass concerning what he said to you, namely, “Let us follow other gods” – gods whom you have not previously known – “and let us serve them.” 13:3 You must not listen to the words of that prophet or dreamer, for the Lord your God will be testing you to see if you love him with all your mind and being. 13:4 You must follow the Lord your God and revere only him; and you must observe his commandments, obey him, serve him, and remain loyal to him. 13:5 As for that prophet or dreamer, he must be executed because he encouraged rebellion against the Lord your God who brought you from the land of Egypt, redeeming you from that place of slavery, and because he has tried to entice you from the way the Lord your God has commanded you to go. In this way you must purge out evil from within.

False Prophets in the Family

13:6 Suppose your own full brother, your son, your daughter, your beloved wife, or your closest friend should seduce you secretly and encourage you to go and serve other gods that neither you nor your ancestors have previously known, 13:7 the gods of the surrounding people (whether near you or far from you, from one end of the earth to the other). 13:8 You must not give in to him or even listen to him; do not feel sympathy for him or spare him or cover up for him. 13:9 Instead, you must kill him without fail! Your own hand must be the first to strike him, and then the hands of the whole community. 13:10 You must stone him to death because he tried to entice you away from the Lord your God, who delivered you from the land of Egypt, that place of slavery. 13:11 Thus all Israel will hear and be afraid; no longer will they continue to do evil like this among you.

Proverbs 30:6

30:6 Do not add to his words,

lest he reprove you, and prove you to be a liar.

Revelation 22:18-19

22:18 I testify to the one who hears the words of the prophecy contained in this book: If anyone adds to them, God will add to him the plagues described in this book. 22:19 And if anyone takes away from the words of this book of prophecy, God will take away his share in the tree of life and in the holy city that are described in this book.