The meaning of this verse is closely linked to the preceding verses. Some follow the Septuagint and incorrectly understand that it is Jonathan who makes a commitment to David, as in “Jonathan then renewed his oath to David” (so New Jerusalem Bible).

But Critique Textuelle de l’Ancien Testament, which gives a {B} rating to the Masoretic Text, provides a clear explanation. In verse 16 Jonathan has obtained an oath, or promise, from David. Now in verse 17 Jonathan makes David swear an oath again, this time guaranteeing the oath by the love that he has for Jonathan. Good News Translation incorrectly says that Jonathan “made David promise to love him.” But Jonathan does not ask David to promise to love him. Rather, he asks David to promise to keep the covenant with Jonathan’s descendants and asks David to guarantee this by swearing on the basis of his love for Jonathan (by his love for him). Compare Parola Del Signore: La Bibbia in Lingua Corrente, “Jonathan made David swear again in the name of his friendship; he loved him more than a brother.” In some cases the meaning of swear again may have to be filled out to say something like “promise that he would be kind to his descendants.”

For he loved … his own soul: literally “for love of his nefesh he loved him.” Nefesh here stands for a person’s whole being. A literal translation will be obscure in many languages. In some languages the best translation will be the reflexive pronoun “himself” as in Good News Translation and other modern versions. Others may say “his own life.” It may also be necessary to make clear that the subject of the verb loved is Jonathan, as in Good News Translation. See the similar statement in 18.1, 3.

Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on the First and Second Books of Samuel, Volume 1. (UBS Helps for Translators). New York: UBS, 2001. For this and other handbooks for translators see here .