How can one explain the mutual love between David and Jonathan? Between them there was this close bond which united them – the same faith. Each of them had demonstrated this faith by winning all by himself a victory for the LORD over the Philistines.
It is because they have in common a “like precious faith” that Christians recognize and love each other (2 Peter 1:1). Let us remember this when we choose our friends. For us, as children of God, it is not possible to have a true and deep friendship with someone who does not share the same faith in the Lord Jesus Christ.
Once again, Jonathan, not without risk, acts as advocate for David with his father Saul. Saul, unbelieving, has forgotten the LORD’s judgment on him (1 Samuel 13:13-14). And, despite this, he would like to ensure the right of his son to the royal succession (v. 31). Jonathan thus seems to be acting against his own interests. This is the sign of true love (see 1 Corinthians 13:5). Even after his father has tried to kill him too, if he is grieved, it is because of the outrage against David and not at all for himself (v. 34). Dear friends, do the outrages committed by the world against the Lord Jesus grieve us more than the wrongs which it can do to us ourselves?
– From Read Through the Bible in a Year with commentary by Jean Koechlin