1 Samuel 19:9-10
9 But an evil spirit from the Lord came on Saul as he was sitting in his house with his spear in his hand. While David was playing the lyre, 10 Saul tried to pin him to the wall with his spear, but David eluded him as Saul drove the spear into the wall. That night David made good his escape.
If God is good and righteous without any sin (Psalms 92:15) why would He send an evil spirit, demon to attack Saul which in turn tried to kill the one God anointed as king and the line of which Jesus was going to come from?
Let’s take a look at some passages in the Book of Job that will give some light to this question.
6 One day the angels came to present themselves before the Lord, and Satan also came with them. 7 The Lord said to Satan, “Where have you come from?”
Satan answered the Lord, “From roaming throughout the earth, going back and forth on it.”
8 Then the Lord said to Satan, “Have you considered my servant Job? There is no one on earth like him; he is blameless and upright, a man who fears God and shuns evil.”
9 “Does Job fear God for nothing?” Satan replied. 10 “Have you not put a hedge around him and his household and everything he has? You have blessed the work of his hands, so that his flocks and herds are spread throughout the land. 11 But now stretch out your hand and strike everything he has, and he will surely curse you to your face.”
12 The Lord said to Satan, “Very well, then, everything he has is in your power, but on the man himself do not lay a finger.”
As you can see from the verses above Satan asked God permission to attack Job and see if he can make Job curse God. Satan thought that Job’s love for God was based on God’s blessing towards him. God wanted to show Satan that true love doesn’t hinge on material blessings from Him but from the individual sincerely recognizing that He is good, loving and no one else can save but Him alone. Only God deserves worship, honor, glory and thanksgiving.
The phrase “an evil spirit from the Lord” simply means that God allows the enemy to attack the person for the purpose of testing and refinement of their faith.
The evil spirit wasn’t concerned in tormenting Saul but used Saul’s torment to have David come in into Saul’s presence and play the musical instrument to get an opportunity to kill the one the Lord anointed. That was the evil spirit’s true intent. God allowed this attack on David so that he would learn to depend on Him. The Psalms that David wrote was the fruit of king Saul’s pursuit in trying to take his life.
Another example of why God allows the enemy to attack a believer is found in Luke 22:31 which says, 31 “Simon, Simon, Satan has asked to sift all of you as wheat. 32 But I have prayed for you, Simon, that your faith may not fail. And when you have turned back, strengthen your brothers.”
Satan asked permission to sift Peter which occurred when Peter denied knowing Jesus 3 times but through that experience, after Peter repented his faith was strengthened which in turn helped his brothers through their weaknesses for the task of taking the gospel to all nations.
God is not the One who sends an evil spirit for the purpose of causing harm to a person but the evil spirit comes to God and asks permission to attack Christians. The enemy thinks that he will hurt us but God turns the enemy’s attack around to strengthen us.