Revelation 22:18-19

"I testify to every one who hears the words of the prophecy of this book, if anyone shall add to them, God will add to him the plagues that are written in this book;

Matthew 28:20

teaching them to observe all things, whatsoever I commanded you; and, behold, I am with you all the days, even to the end of the age."

Treasury of Scripture Knowledge

Summary

What thing soever I command you, observe to do it: thou shalt not add thereto, nor diminish from it.

Bible References

Thou shalt not

Matthew 28:20
teaching them to observe all things, whatsoever I commanded you; and, behold, I am with you all the days, even to the end of the age."
Revelation 22:18
"I testify to every one who hears the words of the prophecy of this book, if anyone shall add to them, God will add to him the plagues that are written in this book;