What the passage says
The account is blunt. After the Spirit of the Lord departed from Saul, the text says an evil spirit from the Lord troubled him (1 Samuel 16:14). The Bible connects Saul's distress with God's judgement, so it shouldn't be explained away.
At the same time, this does not mean God became evil or tempted Saul to sin. The Hebrew word translated evil can also describe something harmful, troubling, or calamitous. The passage presents a spirit that brought Saul real distress, while making clear that it remained under God's authority.
But the Spirit of the Lord departed from Saul, and an evil spirit from the Lord troubled him.
Saul had rejected God's word
This did not follow one ordinary failure. Saul repeatedly chose his own judgement over God's clear command. When Saul spared what God had told him to destroy, Samuel confronted him and said that rebellion was a serious rejection of God's word (1 Samuel 15:23). Samuel then told Saul that the Lord had rejected him as king (1 Samuel 15:26).
Saul was sorry about losing honour before the people, but the story does not show the humble turning back to God that marked David's life when he sinned. Saul wanted to keep his position. His heart was already becoming fearful, controlling, and resistant to correction.
For rebellion is as the sin of witchcraft, and stubbornness is as iniquity and idolatry. Because thou hast rejected the word of the Lord, he hath also rejected thee from being king.
God rules, but does not do evil
Saying the spirit was from the Lord shows that no spiritual power operates outside God's rule. God used this painful affliction as part of his judgement on Saul and his transition of the kingdom to David. Still, God's sovereign authority over an event is not the same as approving evil or creating sinful desires in a person.
James says God does not tempt anyone to evil (James 1:13). Saul's jealousy, rage, and choices belonged to Saul. Later, when David's music was bringing him relief, Saul cast a javelin at David (1 Samuel 18:10-11). The troubling spirit did not remove Saul's responsibility for violence.
Let no man say when he is tempted, I am tempted of God: for God cannot be tempted with evil, neither tempteth he any man:
There was mercy in Saul's distress
Even here, the story contains a surprising kindness. David was brought to Saul, and his harp playing brought Saul relief for a time (1 Samuel 16:23). God was preparing David to become king, yet Saul was not left without moments of peace.
This passage warns us not to harden ourselves when God corrects us. But it does not give permission to call every experience of anxiety, depression, illness, or inner pain a spiritual punishment. Scripture does not let us make that judgement about another person. Someone who is struggling deserves compassionate prayer, trusted support, and appropriate care.
Some details remain mysterious, and it is okay to say so. What is clear is that God judged Saul's persistent rebellion, remained in control, and continued moving his purposes forward through David.