"Now the Spirit of the Lord had departed from Saul, and an evil spirit from the Lord tormented him".
And again (same book) 18:10
"The next day an evil spirit from God came forcefully upon Saul".
It is the phrase "from the Lord" and "from God" in these verses that has me puzzled. I just never saw anything like that before and wondered if it ocurred in other places and what exactly it means.
My footnotes (Life Application Bible) is vague in explanation. Here is what it says: "What was the evil spirit the Lord sent? Perhaps Saul was simply depressed. Or perhaps the Holy Spirit had left Saul, and God allowed an evil spirit (a demon) to torment him as judgement of his disobedience (this would demonstrate God's power over the spirit world). Either way, Saul was driven to insanity, which led him to attempt to murder David".
That is what my footnotes say, but I still find that passage difficult.