The word used for ”prophesied” is from the Hebrew conjugation ”Hith-pael”. That conjugation is used for a corrupt or imitated prophecy. A true and real prophecy should have used ” Niphal”. Elicots commentary recognises this difference. ” Saul was in a state of phrenzy, unable to master himself, speaking words of which he knew not the meaning, and acting like a man possessed. In all this there was something akin to the powerful emotions which agitated the true prophet: only it was not a holy influence, but one springing from violent) passions.” We see these kind of demonstrations in prayer houses. Some of them are so much and so mean that the drama is more than even the message. This demonic oppression was possible because Saul became envious of David. God only permitted these demonic oppression on Saul. He never caused it. Sin is the fertile ground for demonic oppression. Out of the abundance of his heart, Saul launched the javelin at David. That couldn’t have been God. Twice, God protected David. In this same way, may God protect you from every satanic arrows or javelins shot at you. In Jesus Name.
And it came to pass on the morrow, that the evil spirit from God came upon Saul, and he prophesied in the midst of the house: and David played with his hand, as at other times: and there was a javelin in Saul’s hand. And Saul cast the javelin; for he said, I will smite David even to the wall with it. And David avoided out of his presence twice. 1 Samuel 18:10-11 KJV