I Samuel - Chapter 16
Here Comes David!
G-d told Shmuel to "get over" Shaul because He was sending him to anoint his successor, one of the sons of Jesse of Bethlehem. Shmuel was concerned that Shaul would find out and try to kill him. (Yes, Shmuel had faith that G-d would protect him, but one cannot rely on miracles; due diligence must be taken.) G-d told Shmuel to take a cow as an offering. With this pretext, he would invite Jesse's family to the feast.
Arriving in Bethlehem, Shmuel invited all the city elders, including Jesse, to partake in his feast. When he saw Jesse's oldest son, Eliav, he was convinced that this must be Hashem's chosen one. "Not so fast!" G-d said. "Don't look at the outside; only I can see what's on the inside!" After that, Shmuel wasn't so hasty. He looked at Avinadav, Shammah and the other sons of Jesse and knew that none of them were the one. "Have you no other sons?" Jesse sent for the youngest of his eight sons, David, who was tending the sheep. G-d informed Shmuel that David was, in fact, the one and Shmuel anointed him.
Meanwhile, Shaul started suffering from an "evil spirit," a melancholy that we might call clinical depression. Music having charms, his servants looked for someone to play the harp and settle Shaul's troubled spirit during these episodes. Who did they recommend but the same David who, unknown to them, was just anointed Shaul's successor! Shaul sent for David and came to like him very much. His harp-playing calmed Shaul's nerves and Shaul made him his armor bearer. At this point, Shaul gave David a regular job, although David still went home periodically, to help with the family business, as we shall see.