Saul has tried unsuccessfully to put David into impossible situations where the Philistines would kill him. Saul even gave one of his daughters, Michal, to David as his wife in hopes that she would help bring David’s reputation and success down. But, instead David’s marriage to the king’s daughter only made him more popular and secured a position as a possible successor to Saul on the throne.
Everything Saul does to try to harm David backfires on him and advances David. After multiple attempts to derail David’s success and popularity Saul finally resorts to another physical attack. David had just returned from stopping another Philistine advance into Israeli territory when he and Saul where hanging out in the palace while David played on the lyre. For the second time Saul tries to kill David himself with a spear. David, who was most likely anticipating some form of attack, reacted quickly, dodged the attack and escaped.
The word “escape” or “fled” is nas wayyimmalet. This word marks a turning point in the life of David and a permanent change in his relationship with Saul and the public’s understanding and opinion of David’s motives. David will never return to Saul but will spend the rest of his time under Saul’s reign on the run and hiding.
The concept of an “evil spirit” coming from the Lord is the result of Saul’s rebellion against the Lord and Saul’s rejection of the God’s Word. This is not saying the Lord is evil nor that the Lord desires evil, but when men create a vacuum by separating themselves from God through sin and rebellion the presence of evil is brought into the situation. (Also, consider the days of Abimelech’s sin in Judges 9:23.)