Herbert W. Armstrong's booklet, Just What do you Mean the Unpardonable Sin?, suggests that a root of bitterness is a major contributory cause of the unpardonable sin. The root the apostle Paul warns against derives from resentment or a grudge against a brother as well as neglecting spiritual tools, allowing one to turn away from God, poisoning the mind and skewing his perceptions. God gives grace, but He can withhold it as well if we allow bitterness about our circumstances to poison us. Roots of bitterness can tap into neglect, worldly associations, or other diversions, defiling our spiritual outlook.