And it came to pass, when the [evil] spirit from God was upon Saul,.... See 1Sa 16:14 though the word evil is not in the text here; wherefore Abarbinel thinks that this here was the Spirit of God, which stirred up in him thoughts of divine things, put him in mind of what God had said, that he had rejected him from being king, and had rent the kingdom from him; and this filled him with grief and trouble, and he became melancholy:that David took an harp, and played with his hands; upon it; and, as Josephus says, at the same time sung hymns and psalms; made use both of vocal and instrumental music:so Saul was refreshed, and was well; became cheerful, his grief was removed, his black and gloomy apprehensions of things were dispersed, and he was cured of his melancholy disorder for the present:and the evil spirit departed from him: at least for a while; he had his fits and intervals; of the effects of music in a natural way,See Gill on "1Sa 16:16", though no doubt the music of David was more than natural, being attended with the power and blessing of God, in order to raise his fame and credit at court.
Ut supra. (Antiqu. l. 6. c. 8. sect. 2.