15 See to it that no one falls short of the grace of God and that no bitter root grows up to cause trouble and defile many.

Read Hebrews 12:15 Using Other Translations

Looking diligently lest any man fail of the grace of God; lest any root of bitterness springing up trouble you, and thereby many be defiled;
See to it that no one fails to obtain the grace of God; that no "root of bitterness" springs up and causes trouble, and by it many become defiled;
Look after each other so that none of you fails to receive the grace of God. Watch out that no poisonous root of bitterness grows up to trouble you, corrupting many.