1 Samuel 16:22

but David went back and forth from Saul to shepherd his father’s flock at Bethlehem.

Now when Saul saw David going out to meet the Philistine, he said to Abner the commander of the army, “Abner, whose son is this young man?” And Abner said, “By your life, O king, I do not know.”

And the king appointed for them a daily ration from the king’s choice food and from the wine which he drank, and appointed that they should be educated three years, at the end of which they were to stand before the king.