Now the Spirit of Yahweh departed from Saul, and an evil spirit from Yahweh troubled him.
"And David came to Saul and entered his service"  (1 Samuel 16:21). "This is a summary of developments that, "undoubtedly covered several weeks or months."[13] It is impossible to view this paragraph as a chronological arrangement of events in an orderly sequence.  It was written to give a quick glance at what would take place in David's future.  "O.T. authors not infrequently pursue a theme to its ultimate consequences, and then return to fill in the details";[14] and there is a lot of that in Samuel.