In 2 Samuel 9 we learn the story of Mephibosheth, the crippled son of Davids friend Jonathon. He was crippled but he was also part of the old regime. As a new King and leader of a new regime it would be custom for David to eliminate Mephibosheth as a rival to the throne. Instead David honors Mephibosheth and honors the promise he made to his old friend Jonathon.