After David defeated the giant Goliath and rallied the armies of Israel to attack and defeat the Philistines, a song was popularized and sung by the women of Israel:
“Saul has struck down his thousands, and David his ten thousands.” (1 Samuel 18:7)
We learn later on that this song was so popular that it even spread among the Philistines (21:11), the very people who were the thousands and ten thousands being struck down in the song. Upon hearing this song, King Saul grows jealous of David’s growing popularity. “What more can he have but the kingdom?” (18:8) Saul asks rhetorically. After this point, Saul attempts to pin David with a spear multiple times, sends David out on suicide missions (all of which David returns victorious and even more popular than before), and eventually leads to multiple periods of time where Saul pursues David across Israel to kill him.
It shouldn’t have been that way, of course.