12 Then Jonathan told David, "I promise by the Lord, the God of Israel, that by this time tomorrow, or the next day at the latest, I will talk to my father and let you know at once how he feels about you. If he speaks favorably about you, I will let you know. 13 But if he is angry and wants you killed, may the Lord strike me and even kill me if I don't warn you so you can escape and live. May the Lord be with you as he used to be with my father. 14 And may you treat me with the faithful love of the Lord as long as I live. But if I die, 15 treat my family with this faithful love, even when the Lord destroys all your enemies from the face of the earth." 16 So Jonathan made a solemn pact with David, saying, "May the Lord destroy all your enemies!" 17 And Jonathan made David reaffirm his vow of friendship again, for Jonathan loved David as he loved himself.
Matthew Henry's Commentary on 1 Samuel 20:12-17
Commentary on 1 Samuel 20:11-23
(Read 1 Samuel 20:11-23)
Jonathan faithfully promises that he would let David know how he found his father affected towards him. It will be kindness to ourselves and to ours, to secure an interest in those whom God favours, and to make his friends ours. True friendship rests on a firm basis, and is able to silence ambition, self-love, and undue regard for others. But who can fully understand the love of Jesus, who gave himself as a sacrifice for rebellious, polluted sinners! how great then ought to be the force and effects of our love to him, to his cause, and his people!