Question:

What does “the evil spirit from LORD” means as stated in 1 Samuel 19:9?

Answer:

It is a truism that everything which happens is either caused by God or
allowed by God. In the case of evil, God allows bad things to happen
because such things fall under the free will God has given to us and, I
believe, has also given to angelic beings. Evil is the indirect result of
God giving those he loves the freedom to do good or to do evil. This idea
of God allowing Satan or an evil spirit free reign to work in a way which
even God can ultimately use is found in Job 1:6-12. Here, God allows
Satan to test Job to do evil. In this case, God does not tempt Job. God
does not tempt us to do evil (James 1:13-15), but God does allow Satan to
tempt us. He does allow us to give in to our own evil desires, which can
entice us and lead to sin (paraphrasing James 1). God will even allow an
evil spirit to enter a person. Possession by evil spirits is a reality
which Jesus clearly acknowledged.

Based on this, I believe that what we see in 1 Samuel 19:9 is an example
of God allowing a thing to happen which he is not causing to happen. Saul
had alread hardened his heart. Saul had for a long time been disobeying
God and giving in to the sin of pride (for example, see 1 Samuel 15).
Saul’s heart had become so hardened, that, as a discipline, God allowed an
evil spirit to come upon Saul and to “possess” Saul. This evil spirit
caused Saul to attack David and to act in ways which the modern mind would
describe as psychotic behavior. Whether we view this as demon possession
or as Saul having psychotic episodes may not change the result of the
behavior all that much.

God allowed (but did not cause) an evil spirit to overcome Saul. That is
what explains 1 Samuel 19:9.

John Oakes, PhD