Shortly after Saul takes David into his service, we read:
The next day an evil spirit of God gripped Saul and he began to rave in the house, while David was playing [the lyre], as he did daily. Saul had a spear in his hand, and Saul threw the spear, thinking to pin David to the wall. But David eluded him twice.—1st Samuel 18:10-11 (NJPS)
I see two ways to read this:
- Saul attacked David twice on one occasion (perhaps with two different spears) or
- Saul attacked David on two separate occasions.
Also, why didn't this cause problems with the two men's relationship? Later in the chapter, David becomes engaged to Saul's daughter Merab and, when that fell through, to his other daughter Michal.