What does the Bible say about resentment and bitterness?

from the old testament

• Resentment is as old as Genesis 4. Cain was angry that God accepted Abel's sacrifice and not his own (Genesis 4:4–5). Instead of actively dealing with those feelings by admitting his own part in the situation and considering God's point of view, he buried his anger under feelings of resentment which grew until he killed his brother (Genesis 4:8). God had warned him that his anger would consume him if he didn’t master it (Genesis 4:6–7).
• Mankind followed Cain's example throughout the years. Sarai asked Abram to impregnate her maidservant Hagar, then resented Hagar when it worked (Genesis 16:4–6).
• Leah and Rachel's resentment regarding their fertility created a baby-war that didn't end until Jacob had conceived thirteen children by four different women (Genesis 29:31—30:24; 35:16–26).
• When King Saul realized how much the people loved David and celebrated his accomplishments, Saul resented David so much he tried to kill him with a spear multiple times (1 Samuel 18—19). David ultimately left Jerusalem, and Saul continued to pursue him for years, even employing the best of his army to kill David (1 Samuel 20—31).
• The epitome of bitterness in the Bible is Job's wife. Anger would be an understandable reaction to God allowing her children to die and her family's assets to be taken. But instead of accepting God's sovereignty like Job did or even being honest and talking to God, she allowed anger to lead to resentment, which molded her character into bitterness. The apex occurred in Job 2:9 when she told Job, "Do you still hold fast your integrity? Curse God and die."
• Bitterness is easy to fall into, but it is also possible to reject bitterness and return to faith in God. In Ruth 1:20, having lost her husband and two sons, Naomi tells her daughters-in-law to call her Mara, which means "bitter," saying, "for the Almighty has dealt very bitterly with me." The devotion of Ruth, however, redirected Naomi's anger to action, and God restored Naomi and redeemed her story as she became nurse to Ruth's son, the grandfather of King David.
• King David also escaped the trap of bitterness. In 1 Samuel 30, David and his men returned to the city where they had been staying to find their wives and children taken captive. Verse 6 says, "And David was greatly distressed, for the people spoke of stoning him, because all the people were bitter in soul, each for his sons and daughters. But David strengthened himself in the LORD his God." Instead of resenting God, David used many such occasions to write what he was feeling, composing much of the book of Psalms.

from the new testament

• Perhaps the most significant example of resentment and bitterness in the New Testament is that of the Jewish religious leaders who demanded Jesus' death (Mark 14:1–2; 15:10; John 9:22).
• Bitterness and resentment spring from a belief that someone, often God, is being unfair or not giving what is due. Peter recognized this in Simon the Magician in Acts 8:14–24. Simon wanted the power that Peter and John wielded—even offering to pay for it. But Peter saw a "gall of bitterness" behind Simon's request.
• The Bible tells us to reject bitterness. Ephesians 4:31 says, "Let all bitterness and wrath and anger and clamor and slander be put away from you, along with all malice."
• Hebrews 12:15 says, "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."
• James 3:13–18 warns that words spoken in bitterness have nothing to do with wisdom but are "earthly, unspiritual, demonic."

implications for today

It's easy to resent God when we see Him blessing others while we suffer (Psalm 73). If we feed our resentment long enough, it will lead to a bitter attitude. We'll begin to see everything as a hardship—even blessings that God tries to give us. Eventually, we won't be able to see His work in our lives at all.

The most effective way to deal with resentment and bitterness is to appropriately handle the anger that comes first. Anger is a natural, sometimes physiological, response, but left unchecked it can do great damage. It can blind us to our part in the situation. It can push out all empathy for and understanding of others. Even when our anger is just, we must not let it control our actions or beliefs. Taking every thought captive (2 Corinthians 10:5) and submitting to God (James 4:7) will drive us to forgive others (Colossians 3:13) and keep our anger from turning to resentment. God can heal resentment and bitterness if we let Him. He can heal our hearts and turn us to forgiveness of others and trust in Him.