v1-4: After the fight between David and Goliath, Abner brought David to Saul (17.55-58). Saul was very pleased; the enemy had been defeated, and his own impotence had been covered up; day after day Goliath had taunted Israel, but Saul had no answer.
God had vindicated His own Name, but through David, not Saul. If God does not use us, He will use someone else.
Jonathan was doubtless impressed by David's bravery. Jonathan may not have been allowed to challenge Goliath, as Saul was preparing him to be the next king (See 20.31). Jonathan also gave David much, an indication of their comparative wealth.
v5-7: David's initial popularity; he was faithful, he was successful, he was respected and loved by the people; he became the theme of the people's songs. In a similar way, the Lord Jesus was very popular during the early part of His ministry.
v8-9: The women's song led to jealousy in Saul; he did not rejoice that another was blessed.
v10-11: Circumstances were brought together; the evil spirit upon Saul, David playing music, since he had remained with Saul (v2), and Saul's jealousy; this led to Saul's attack upon David. This gives us further insight into Saul's unstable condition, and his further downward spiral.
David left the palace, and Saul's presence. In a similar way, the Lord Jesus was driven out into the wilderness.
v12-16: Saul saw that God had blessed David, and that David continued to grow in popularity. Saul became afraid of him, and schemed to have him destroyed.
v17: Saul's next scheme was to have David killed by the Philistines. David himself used a similar ruse to have Uriah killed (2 Sam 11.14).
v18-19: David was humble and innocent; he did not seek position for himself. This godly, principled stand compares with that of Joseph and Daniel, who were both young men. Saul struggled to cope with this attitude, expecting David to have desires like his own.
v20-22: Conveniently, Saul's daughter loved David, and Saul used that to try to destroy David. He sent messengers to speak privately with David, offering him Michal's hand in marriage. Here was a snare to catch David, 2 Cor 2.11; Eph 6.11.
v23: David's continued humility; he was not a suitable match for the king's daughter.
v24-26: The second part of Saul's plan was to have Philistines killed. David had no problem with this, as they were the enemies of God, and of His people. It was this that convinced David that he could become the king's son-in-law.
v27-30: Saul's plan back-fired; David successfully killed 200 Philistines, he counted the foreskins before Saul, and was married to Michal. Even as Michal's husband, David lived a consistent, faithful life. Again, the writer notes, Saul grew afraid of David, hating his success, envying the blessing of God upon him.