I gotta have my orange juice.

Pursue peace with all people, and holiness, without which no one will see the Lord: looking carefully lest anyone fall short of the grace of God; lest any root of bitterness springing up cause trouble, and by this many become defiled; lest there be any fornicator or profane person like Esau, who for one morsel of food sold his birthright. (Heb. 12)

Given how we use the word bitterness today, it’s easy to assume this refers to our attitude toward fellow believers. But the Biblical use of this word is broader and has to do with poisonous teaching and conduct. Thus:

“I make this covenant and this oath . . . so that there may not be among you man or woman or family or tribe, whose heart turns away today from Yahweh our God, to go and serve the gods of these nations, and that there may not be among you a root bearing bitterness or wormwood; and so it may not happen, when he hears the words of this curse, that he blesses himself in his heart, saying, ‘I shall have peace, even though I follow the dictates of my heart’—as though the drunkard could be included with the sober.” (Deut. 29)

Then the third angel sounded: And a great star fell from heaven, burning like a torch, and it fell on a third of the rivers and on the springs of water. The name of the star is Wormwood. A third of the waters became wormwood, and many men died from the water, because it was made bitter. (Rev. 8)

[Moses] afterwards explained what he meant, that is, lest any one, felicitating himself in sin, and like the drunken who are wont to excite thirst, stimulating sinful desires, should bring on a contempt of God through the alluring of hope of impunity. The same is what the Apostle speaks of now; for he foretells what will take place, that is, if we suffer such a root to grow, it will corrupt and defile many. (Calvin)

[The apostle] enters a serious caveat against apostasy. Here you may observe . . . the consequences of apostasy: where persons fail of having the true grace of God, a root of bitterness will spring up, corruption will prevail and break forth. (Matthew Henry)

One such poisonous teaching is the teaching that it does not matter greatly whether or how we obey God’s law and serve him. It is true that we have no reason to boast in our belonging to God (Deut. 9), but it is false that obedience is a light matter (Deut. 28).

And having been perfected, He became the author of eternal salvation to all who obey Him. (Heb. 5:9)