1 Corinthians 15:15

And also, we are found to be false witnesses about God because we testified that God raised up Christ [from the dead], when [in reality] He did not raise Him up if, in fact, the dead are not raised up.

Revelation 22:18-19

I testify to every person who hears the words of the prophecy of this book [Note: This is probably Jesus speaking, but could possibly be John]. If anyone adds to these words, God will add to him the calamities described in this book.

Treasury of Scripture Knowledge

Summary

Add thou not unto his words, lest he reprove thee, and thou be found a liar.

Bible References

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Revelation 22:18
I testify to every person who hears the words of the prophecy of this book [Note: This is probably Jesus speaking, but could possibly be John]. If anyone adds to these words, God will add to him the calamities described in this book.

And

1 Corinthians 15:15
And also, we are found to be false witnesses about God because we testified that God raised up Christ [from the dead], when [in reality] He did not raise Him up if, in fact, the dead are not raised up.