NASB
Proverbs 30:6 Do not add to His words
Or He will reprove you, and you will be proved a liar.
Deuteronomy 4:2 "You shall not add to the word which I am commanding you, nor take away from it, that you may keep the commandments of the LORD your God which I command you
Deuteronomy 12:32 "Whatever I command you, you shall be careful to do; you shall not add to nor take away from it.
Revelation 22:18 I testify to everyone who hears the words of the prophecy of this book: if anyone adds to them, God will add to him the plagues which are written in this book;
It is clearly that it said, do not add. Do you know why it is appears in the bible? Catholic, , Muslim or whatever other than Christian. They add more laws or verses to do something different what the Holy-Bible said. For example, “Justification.” All other religious disagree with Justification because they think it is so easy to do it.
Therefore, Catholic added to have Justification is through good works. It is clearly that Catholic is adding their Bibles. Therefore, Jesus Christ was talking to Catholic about that situation. Catholic worships Mary Virgin and Jesus Christ. Jesus Christ said do not idol other than me at 1st Commandment. Catholic seems remove that and add Mary Virgin. That is why Catholic is twisting the bible to meet the human's satisfaction than the God's want. Do you understand? Whole Bible translation isn’t like that and they are just changing the words to meet the people’s need with their language level at same meaning and points from the Hebrew and Greek bible.
If you are wondering, what is Justification? Put whole your faith on Jesus Christ (believe in Jesus Christ as your savior) and walk with him (repent the sin) and Jesus Christ will pours his blood of righteous covered on you (Salvation). So the God will look at you as righteous even you are sinners because Jesus Christ had his blood on you to make yourself looks a like righteous (holy person). Completely of your sins are thrown on the Jesus Christ’s cross and Jesus Christ forgives your sins because Jesus Christ poured his grace on you. Therefore, you can join Jesus Christ’s paradise (Heaven).
Martin Luther and John Calvin, John MacArthur Jr., R.C. Sproul, etc. strongly encourage people to understand the Justification in faith. Many people refuses to believe it because it is so easy. They want to do something that they feel that they deserve his grace.
If you want the verses with Justification in faith and let me know.