Long before David had become king, he had made a promise to his close friend Jonathan. David promised Jonathan that he would always show hesed to Jonathan's descendants (1 Samuel 20:15). This was no small promise because as David was making this promise, he was in competition for the throne with Jonathan's father, Saul, the current king of Israel. To put it simply, despite Jonathan and David's friendship, David and Jonathan's descendants were bound to be political rivals as competing claimants of the throne of Israel. Nevertheless, David binds himself to Jonathan with this promise.
In 2 Samuel 9, David has completed his rise to power as the king of all Israel and Judah. While the narrator of 2 Samuel makes it clear that David was not responsible for the deaths of his political enemies, David's rise to power has still been a violent and bloody affair in which all others with a claim to the throne have been killed. Now David wants to know if there are any descendants of Jonathan to whom he might show hesed as he had promised.
It turns out there is one. He is lame in both feet. His name is Mephibosheth.
It is worth noting the order of Ziba's (David's servant) description of Mephibosheth here. We come to know Mephibosheth's disability before we even know his name. Is this because we always tend to see someone's handicap before we see them as a person? Or is it to assure David that Mephibosheth is not a real military or political threat? Or are we to hear an echo of David's own story in the description of Mephibosheth? When David is first introduced in 1 Samuel 16, like Mephibosheth, he is regarded as a "left-over" of a boy, too young to be considered important, whose name is not even mentioned until he has been anointed by Samuel. Perhaps, we are to hear some mixture of all three of these story lines intertwined together in a complicated mess of good and less honorable intentions as so often happens in real life.
In the end, David keeps his promise to Jonathan and summons Mephibosheth to his royal court. Mephibosheth must have thought this was a summons to his death. As the last living relative of David's political opponents, surely the only reason he would be summoned by the king would be for his execution. But David's covenant with Jonathan completely reverses the parameters of David's relationship to Mephibosheth. Instead of being executed, Mephibosheth is given land and servants and a place at the king's table. This is hesed: a loyalty and faithfulness so great that it relativizes all the other conditions of a relationship.
Of course, David's hesed to Jonathan through Mephibosheth is just a faint image of God's hesed to us. Like Mephibosheth before David, we come before God broken and powerless. We have no claim on this king. He owes us nothing. There is no reason that he should be generous to us... except that he has bound himself to us. And that simple fact changes everything. God has covenanted with us, he has promised us redemption and he is a God who keeps his promises no matter the costs. He is a God of hesed.