12 And Jonathan said to David, "The Lord, the God of Israel, be witness![1] When I have sounded out my father, about this time tomorrow, or the third day, behold, if he is well disposed toward David, shall I not then send and disclose it to you? 13 But should it please my father to do you harm, the Lord do so to Jonathan and more also if I do not disclose it to you and send you away, that you may go in safety. May the Lord be with you, as he has been with my father. 14 If I am still alive, show me the steadfast love of the Lord, that I may not die; 15 and do not cut off[2] your steadfast love from my house forever, when the Lord cuts off every one of the enemies of David from the face of the earth." 16 And Jonathan made a covenant with the house of David, saying, "May[3] the Lord take vengeance on David's enemies." 17 And Jonathan made David swear again by his love for him, for he loved him as he loved his own 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!