Barzillai ventured & volunteered to help king David during the most darkest moment of David's life, while David was running away from his own son Absalom.
2 SAMUEL 19:31-39 [The Life of David]
THE KING REWARDS THE FAITHFUL
David has sinned by committing adultery with Bathsheba and by having her husband killed. God has indicted David for his sin through Nathan the prophet, and David has repented. Nevertheless, there are certain consequences