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. (NIV)
Exercise foresight and be on the watch to look [after one another], to see that no one falls back from and fails to secure God's grace (His unmerited favor and spiritual blessing), in order that no root of resentment (rancor, bitterness, or hatred) shoots forth and causes trouble and bitter torment, and the many become contaminated and defiled by it-- (AMP)
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; (KJV)