And Samuel said unto Saul, I will not return with thee: for thou hast rejected the word of the Lord, and the Lord hath rejected thee from being king over Israel. 1 Samuel 15:26.
When Saul saw that Samuel came no more to instruct him, he knew that the Lord had rejected him for his wicked course, and his character seemed ever after to be marked with extremes. His servants ... at times dared not approach him, for he seemed like an insane man, violent and abusive. He often seemed filled with remorse. He was melancholy, and often afraid where there was no danger.... He was always full of anxiety, and when in his gloomy moods he wished not to be disturbed, and at times would suffer none to approach him.... He would repeat prophetically sayings against himself with distracted energy, even in the presence of his lords and of the people.
Those who witnessed these strange exhibitions in Saul recommended to him music, as calculated to have a soothing influence upon his mind when thus distracted. In the providence of God, David was brought to his notice as a skillful musician....
David's skillful playing upon the harp soothed the troubled spirit of Saul. As he listened to the enchanting strains of music, it had an influence to dispel the gloom which settled upon him, and to bring his excited mind into a more rational, happy state.2Spiritual Gifts 4a:78, 79.
Saul was shorn of his strength, because he failed to make obedience to God's commandments the rule of his life. It is a fearful thing for a man to set his will against the will of God, as revealed in His specified requirements. All the honor that a man could receive on the throne of a kingdom, would be a poor compensation for the loss of the favor of God through an act of disloyalty to heaven. Disobedience to the commandments of God can only bring disaster and dishonor at last. God has given to every man his work, just as truly as He appointed to Saul the government of Israel; and the practical and important lesson to us is to accomplish our appointed work in such a manner that we may meet our life records with joy, and not with grief.3The S.D.A. Bible Commentary 2:1018.
From Conflict and Courage - Page 159