Remember that Jonathan and David were best friends, and in 1 Samuel 20 David promises Jonathan that he will not let his name die. After he has established the kingdom, he wrapped up the loose ends of the promise he made with Jonathan. Not only does David welcome Jonathan’s son Mephibosheth into his own palace to eat at his table, but he returns the land and servants of his grandfather to him.
David kept his promise to Jonathan, even years after Jonathan’s death. He not only allowed Mephibosheth to live, but gave back to him what was rightly his. That is how God fulfills His promises to us through Jesus. Not only does he forgive us, but he gives us the continued promise of His presence in this life and eternal life in the next!