1 Samuel 16:11-13 - And Samuel said to Jesse, “Are these all the children?” And he said, “There remains yet the youngest, and behold, he is tending the sheep.” Then Samuel said to Jesse, “Send and bring him; for we will not sit down until he comes here.” 12 So he sent and brought him in. Now he was ruddy, with beautiful eyes and a handsome appearance. And the Lord said, “Arise, anoint him; for this is he.” 13 Then Samuel took the horn of oil and anointed him in the midst of his brothers; and the Spirit of the Lord came mightily upon David from that day forward.
I imagine if young David were put on a ballot today, few would vote for him. He didn't come from the right type of family, he had no military qualifications, he wasn't an ambassador or a diplomat; and he was more interested in hanging out with sheep than he was with kings. He would be labeled as too young, too inexperienced, unqualified and uneducated.
Yet this is just the type of person God chose to replace Saul. This is the man who would slay a giant, return the ark, defeat countless enemies and be called a man after God's own heart.
But he would not be perfect. Though he strived to serve God, inevitably David would fall short. God's plan would still require something more.
The journey was not yet complete, but the world was a step closer to the Messiah. Samuel journeyed to Bethlehem to anoint a shepherd as king. Generations later, shepherds would journey to Bethlehem to welcome a new King.