181 And it cometh to pass, when he finisheth to speak unto Saul, that the soul of Jonathan hath been bound to the soul of David, and Jonathan loveth him as his own soul. 2 And Saul taketh him on that day, and hath not permitted him to turn back to the house of his father. 3 And Jonathan maketh—also David—a covenant, because he loveth him as his own soul, 4 and Jonathan strippeth himself of the upper robe which 'is' upon him, and giveth it to David, and his long robe, even unto his sword, and unto his bow, and unto his girdle.
Matthew Henry's Commentary on 1 Samuel 18:1-4
Commentary on 1 Samuel 18:1-5
(Read 1 Samuel 18:1-5)
The friendship of David and Jonathan was the effect of Divine grace, which produces in true believers one heart and one soul, and causes them to love each other. This union of souls is from partaking in the Spirit of Christ. Where God unites hearts, carnal matters are too weak to separate them. Those who love Christ as their own souls, will be willing to join themselves to him in an everlasting covenant. It was certainly a great proof of the power of God's grace in David, that he was able to bear all this respect and honour, without being lifted up above measure.