show kindness: The Hebrew word khesed refers to covenant loyalty and faithfulness (steadfast commitment within a relationship). It often describes God’s faithful commitment to his people. It can also describe deep devotion and loyalty between two people.
Here, David uses khesed in a way that echoes the covenant of friendship he made with Jonathan (1 Samuel 20:12–17).
for the sake of Jonathan: David showed kindness because of his promise to Jonathan. Mephibosheth was Saul’s only remaining descendant and Jonathan’s only son.