אַל־תּ֥וֹסְףְּ עַל־דְּבָרָ֑יו פֶּן־יוֹכִ֖יחַ בְּךָ֣ וְנִכְזָֽבְתָּ׃ (פ)
Add thou not unto His words, Lest He reprove thee, and thou be found a liar.
Rashi on Proverbs
lest He prove to you, and you be found a liar He will prove to your face that through your addition you have come to sin, and certainly if you subtract.