1 Samuel 16:15,16 - Joseph Benson’s Commentary on the Old and New Testaments

His servants said, &c. His courtiers could not but observe the change which had taken place in him, and the strange disturbance in his mind, and very probably ascribed it to the hand of God upon him. When the evil spirit from God is upon thee When a melancholy fit seizeth thee. He shall play with his hand, and thou shalt be well And the success confirmed their opinion. It is true, music cannot, of itself, have a direct influence on an evil spirit, to cause it to depart; yet because such a spirit, it seems, had not got possession of him, but only occasionally troubled him, by working on the passions of his mind, and humours of his body; and because it is manifest that music hath great power over these, frequently composing the spirits, and cheering and delighting the mind, and thereby gradually altering, qualifying, and sweetening the very juices and humours of the body; it is not strange if that evil spirit had not that power over Saul when these good effects of music had been experienced by him, which it had had before. Thus Satan had less power over lunatics in the decrease than in the increase of the moon, Matthew 17:15; Matthew 17:18. And seeing music prepared the Lord's prophets for the entertainment of the good spirit, as 2 Kings 3:15, why might it not dispose Saul to the resistance of the evil spirit? and why might not the cheering of his heart, in some measure, strengthen him against those temptations of the devil which were encouraged and strengthened by his melancholy humour? And by this means David, without any contrivance of himself or his friends, is brought to court, soon after he was anointed to the kingdom. Those whom God designs for any service, his providence will concur with his grace to prepare and qualify them for it.