וַיִּכְרֹ֧ת יְהוֹנָתָ֛ן וְדָוִ֖ד בְּרִ֑ית בְּאַהֲבָת֥וֹ אֹת֖וֹ כְּנַפְשֽׁוֹ׃
Then Jonathan made a covenant with David, because he loved him as his own soul.
Read halakhic rulings (Jewish law) on I Samuel 18:3 from the Mishneh Torah and classical halakhic sources, free online.