"Wrath is cruel, and anger is outrageous... " (Prov. 27:4). "... Jealousy is cruel..." (Song of Sol. 8:6).
"Saul eyed David," (but David was not jealous of King Saul). Saul became infuriated at the youth. Murder was in his heart as he cast his javelin at him. Then observing that "the Lord was with David" and that "all Israel loved David," Saul said, "Let the hand of the Philistines be upon him" to slay him!
"Michal, Saul's daughter, loved David," so Saul thought to use her to endanger David's life. Saul proposed that in order for David to become his son-in-law, David should provide 100 foreskins of the Philistines. David actually doubled the number (1 Sam. 18:27). But "...Saul became David's enemy continually." David had won another great victory by slaying many of the Philistines, but instead of honoring David "...Saul sought to smite David even to the wall with the javelin" (1 Sam. 19:10). When Saul saw that all his servants esteemed the name of David to be "precious" he commanded all his servants to kill David! (1 Sam. 18:30 and 19:1). "Jonathan spake good of David unto Saul his father." David was not the adversary, he was the target of Saul's cruel jealousy! "Saul also sent messengers to David's house... to slay him..."! He also "... sent messengers to... bring him... that... he might... slay him..." (1 Sam. 19:15). His unsuccessful efforts to slay David intensified his wrath and in 1 Sam. 19:20 and 21 we see him sending more messengers, three times, and finally "... then went he also..." to slay David (1 Sam. 19:22). Saul was so determined to slay David that he cast a javelin at HIS OWN SON, Jonathan, to smite him, when he sought to dissuade his father (1 Sam. 20:33). How cruel jealousy is!