12 And Jonathan said to David, May the Lord, the God of Israel, be witness; when I have had a chance of talking to my father, about this time tomorrow, if his feelings to David are good, will I not send and give you the news? 13 May the Lord's punishment be on Jonathan, if it is my father's pleasure to do you evil and I do not give you word of it and send you away so that you may go in peace: and may the Lord be with you, as he has been with my father. 14 And may you, while I am still living, O may you be kind to me, as the Lord is kind, and keep me from death! 15 And let not your mercy ever be cut off from my family, even when the Lord has sent destruction on all David's haters, cutting them off from the face of the earth. 16 And if it comes about that the name of Jonathan is cut off from the family of David, the Lord will make David responsible. 17 And Jonathan again took an oath to David, because of his love for him: for David was as dear to him as his very soul.
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!