וַתְּהִי֩ ר֨וּחַ יְהוָ֤ה ׀ רָעָה֙ אֶל־שָׁא֔וּל וְהוּא֙ בְּבֵית֣וֹ יוֹשֵׁ֔ב וַחֲנִית֖וֹ בְּיָד֑וֹ וְדָוִ֖ד מְנַגֵּ֥ן בְּיָֽד׃
And an evil spirit from the LORD was upon Saul, as he sat in his house with his spear in his hand; and David was playing with his hand.
Read kabbalistic (mystical) interpretation of I Samuel 19:9: and classical mystical sources.