Then an evil spirit from the Lord came upon ¹  Saul. He was sitting in his house with his spear in his hand, while David was playing the lyre. ² 

But Saul found out the whereabouts of David and the men who were with him. ¹  Now Saul was sitting at Gibeah under the tamarisk tree at an elevated location with his spear in hand and all his servants stationed around him.

So David and Abishai approached the army at night and found Saul lying asleep in the entrenchment with his spear stuck in the ground by his head. Abner and the army were lying all around him.