| Gill's Exposition of the Entire Bible And Jonathan caused David to swear again,.... Or Jonathan added to make David swears (u); having sworn himself to make a covenant of friendship with David and his family, he moved and insisted on it, that David should swear to keep covenant with him, and his family: because he loved him; it was not so much for the good and safety of his offspring that he made this motion, and was so desirous of renewing and enlarging his covenant with David, as it was his strong love and affection for him; being on that account desirous that there might be the strictest friendship imaginable retained between the two families; or he made him swear by his love to him, as some understand it, which is not so likely; the former sense is better, for he himself sware by the Lord, 1 Samuel 20:12, for he loved him as his own soul; or "with the love of his soul" (w); with the most cordial affection, with a truly hearty and sincere love, see 1 Samuel 18:1. (u) "et addidit", Pagninus, Montanus, Vatablus; so the Tigurine version. (w) "secundum dilectionem animae suae", Pagninus; "amore sui ipsius", Junius & Tremellius.
Keil and Delitzsch Biblical Commentary on the Old Testament"And Jonathan adjured David again by his love to him, because he loved him as his own soul" (cf. 1 Samuel 18:1, 1 Samuel 18:3); i.e., he once more implored David most earnestly with an oath to show favour to him and his house.
Geneva Study BibleAnd Jonathan caused David to swear again, because he loved him: for he loved him as he loved his own soul.
Wesley's Notes 20:17 Swear again - Heb. and Jonathan added or proceeded to make David swear; that is, having himself sworn to David or adjured David, in the foregoing verse , he here requires David's oath to him, by way of restipulation or confirmation. Loved him - Because he had a true friendship for David, he desired that the covenant might be inviolably observed through all their generations.
King James Translators' Notesbecause...: or, by his love toward him
Matthew Henry's Concise Commentary20:11-23 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! | 
