Deuteronomy - Chapter 4
At the start of this chapter Moses gives the following instructions:
“And now, Israel, listen carefully to these decrees and regulations that I am about to teach you. Obey them so that you may live, so you may enter and occupy the land that the Lord, the God of your ancestors, is giving you.2 Do not add to or subtract from these commands I am giving you. Just obey the commands of the Lord your God that I am giving you."
They must listen to the regulations, and also obey them. But also must not add to or subtract from them.
At the end of the book of Revelation - in the final chapter of the Bible, Jesus gives a similar command:
Let anyone who hears this say, “Come.” Let anyone who is thirsty come. Let anyone who desires drink freely from the water of life. And I solemnly declare to everyone who hears the words of prophecy written in this book: If anyone adds anything to what is written here, God will add to that person the plagues described in this book. And if anyone removes any of the words from this book of prophecy, God will remove that person’s share in the tree of life and in the holy city that are described in this book. He who is the faithful witness to all these things says, “Yes, I am coming soon!” Amen! Come, Lord Jesus!