10 Now it came about on the next day that an evil spirit from God came mightily upon Saul , and he raved in the midst of the house , while David was playing the harp with his hand , as usual ; and a spear was in Saul's hand .

Matthew Henry's Commentary on 1 Samuel 18:10

Commentary on 1 Samuel 18:6-11

(Read 1 Samuel 18:6-11)

David's troubles not only immediately follow his triumphs, but arise from them; such is the vanity of that which seems greatest in this world. It is a sign that the Spirit of God is departed from men, if, like Saul, they are peevish, envious, suspicious, and ill-natured. Compare David, with his harp in his hand, aiming to serve Saul, and Saul, with his javelin in his hand, aiming to slay David; and observe the sweetness and usefulness of God's persecuted people, and the barbarity of their persecutors. But David's safety must be ascribed to God's providence.