Here I. David continues his good services to his king and country. Though Saul had requited him evil for good, and even his usefulness was the very thing for which Saul envied him, yet he did not therefore retire in sullenness and decline public service. Those that are ill paid for doing good, yet must not be weary of well doing, remembering what a bountiful benefactor our heavenly Father is, even to the froward and unthankful. Notwithstanding the many affronts Saul had given to David, yet we find him, 1. As bold as ever in using his sword for the service of his country, Sa1 19:8. The war broke out again with the Philistines, which gave David occasion again to signalize himself. It was a great deal of bravery that he charged them; and he came off victorious, slaying many and putting the rest to flight. 2. As cheerful as ever in using his harp for the service of the prince. When Saul was disturbed with his former fits of melancholy David played with his hand, Sa1 19:9. He might have pleaded that this was a piece of service now below him; but a humble man will think nothing below him by which he may do good. He might have objected the danger he was in the last time he performed this service for Saul, Sa1 18:10. But he had learned to render good for evil, and to trust God with his safety in the way of his duty. See how David was affected when his enemy was sick (Psa 35:13, Psa 35:14), which perhaps refers to Saul's sickness.
II. Saul continues his malice against David. He that but the other day had sworn by his Maker that David should not be slain now endeavors to slay him himself. So implacable, so incurable, is the enmity of the serpent against that of the woman, so deceitful and desperately wicked is the heart of man without the grace of God, Jer 17:9. The fresh honours David had won in this last war with the Philistines, instead of extinguishing Saul's ill-will to him, and confirming his reconciliation, revived his envy and exasperated him yet more. And, when he indulged this wicked passion, no marvel that the evil spirit came upon him (Sa1 19:9), for when we let the sun go down upon our wrath we give place to the devil (Eph 4:26, Eph 4:27), we make room for him and invite him. Discomposures of mind, though helped forward by the agency of Satan, commonly owe their origin to men's own sins and follies. Saul's fear and jealousy made him a torment to himself, so that he could not sit in his house without a javelin in his hand, pretending it was for his preservation, but designing it for David's destruction; for he endeavored to nail him to the wall, running at him so violently that he struck the javelin into the wall (Sa1 19:10), so strong was the devil in him, so strong his own rage and passion. Perhaps he thought that, if he killed David now, he would be excusable before God and man, as being non compos mentis - not in his right mind, and that it would be imputed to his distraction. But God cannot be deceived by pretences, whatever men may be.
III. God continues his care of David and still watches over him for good. Saul missed his blow. David was too quick for him and fled, and by a kind providence escaped that night. To these preservations, among others, David often refers in his Psalms, when he speaks of God's being his shield and buckler, his rock and fortress, and delivering his soul from death.

And the evil spirit from the Lord - His envy and jealousy again returned, producing distraction of mind, which was exacerbated by diabolic influence. See on Sa1 16:14 (note).

And the evil spirit from the Lord was upon Saul,.... His melancholy and frantic disorder returned upon those victories of David, and he grew envious, jealous, spiteful, and malicious:

as he sat in his house with his javelin his hand; which either describes the posture he was in when the evil spirit came upon him; or the effects of it, he became dull and melancholy, did not care to go abroad, but kept at home, and was suspicious of everybody; and therefore kept a javelin in his hand to defend himself; or it may be rather to dispatch David with it, when an opportunity should offer, which quickly did:

and David played with his hand; on some instrument of music, particularly the harp, to drive away the evil spirit, the melancholy disorder, from Saul; which showed his humility, that though he was an officer in the army, had a considerable post in it, yet deigned to act the part of a musician to Saul, and his great kindness and affection for him his sovereign, willing to serve him what he could to promote his health and comfort, and the trust and confidence he put in his promise and oath, or rather in the providence of God for his protection in the way of his duty, though he knew how spiteful and injurious Saul had been to him.

SAUL'S MALICIOUS RAGE BREAKS OUT AGAINST DAVID. (Sa1 19:8-17)

David went out, and fought with the Philistines, and slew them with a great slaughter--A brilliant victory was gained over the public enemy. But these fresh laurels of David reawakened in the moody breast of Saul the former spirit of envy and melancholy. On David's return to court, the temper of Saul became more fiendish than ever; the melodious strains of the harp had lost all their power to charm; and in a paroxysm of uncontrollable frenzy he aimed a javelin at the person of David--the missile having been thrown with such force that it pierced the chamber wall. David providentially escaped; but the king, having now thrown off the mask and being bent on aggressive measures, made his son-in-law's situation everywhere perilous.