1 Samuel 18; Romans 16; Lamentations 3; Psalm 34
the kind of jealousy described in 1 Samuel 18 is a terrible thing.
(1) It is grounded in an ugly self-focus, a self-focus without restraint. In his world, Saul must be number one. This means that peers must not best him or he becomes jealous. Not for an instant does he look at anything from the perspective of others—David’s perspective, for instance, or Jonathan’s. Ultimately, he cannot look at anything from God’s perspective either. His self-focus belongs to the genus of self-centeredness that lies at the heart of all human sinfulness, but in its degree and intensity it is so unrestrained that it simultaneously loses touch with reality and adopts the most elemental idolatry.
(2) It is triggered by endless comparisons, endless assessments of who’s up and who’s down. Thus if David’s successes redound well on Saul, Saul is pleased; but if someone starts making comparisons between Saul and David that are in any way invidious to Saul, he is jealous (18:7–8). Insofar as David’s successes are an index of the fact that “the Lord was with David” (18:12–28), Saul is jealous because he knows that the Lord is not with him. The tragedy is that this recognition does not breed repentance, but jealousy. Even the love Saul’s daughter Michal has for David exacerbates Saul’s jealousy (18:28–29). Inevitably, this kind and degree of jealousy is very much bound up with fear; again and again we are told that Saul feared David (18:12, 15, 29). David has become an unbearable threat. Jealousy of this order cannot tolerate competence in others.
It has to be said that many leaders, not least Christian leaders, even when they do not succumb to this degree of malevolence, fill the positions around them with less competent people, thinking that they thereby preserve their own image or authority. They don’t, of course; they simply become masters of incompetent administrations. On the long haul, their own reputations are diminished. But jealousy is such a blinding sin that such obvious realities cannot be admitted.
(3) In the worst cases, this sort of jealousy is progressively devouring. It nags at Saul’s mind and multiplies like a cancer. It erupts in uncontrolled violence (18:10–11); it slips into twisted schemes enmeshing Saul’s own family (18:20–27). In the chapters ahead it settles into something beyond rage—implacable hatred that deploys the armed forces against one innocent man who makes Saul feel insecure.
A believer who above all wants the name of the Lord to be exalted, who genuinely desires the good of the people of God, and who is entirely content to entrust his or her reputation to God, will never succumb to the sin of jealousy.
 Carson, D. A. (1998). For the love of God: a daily companion for discovering the riches of God’s Word. (Vol. 1, p. 25). Wheaton, IL: Crossway Books.