12:15 The readers are responsible to each other, to watch out for one another so “no one fails to obtain” God’s grace (cf. 4:1).

root of bitterness. In Deut. 29:18, the “root bearing . . . bitter fruit” is a person who spreads doubt and disloyalty toward the Lord among the covenant people. Here, too, this “root of bitterness” is a person who “causes trouble” and causes others to be “defiled.” To sustain each other’s faith, we must encourage the weak, but also oppose apostates, who may influence others.