Midrasz do Samuela I 16:11

"He and Hoshea the son of Nun": Is it not written (Numbers 13:16) "And Moses called Hoshea the son of Nun 'Yehoshua'"? Why, then, is it written here "he and Hoshea the son of Nun"? To teach us the righteousness of Yehoshua. I might think that his head "swelled" with his new-found authority; it is, therefore, written "he and Hoshea the son of Nun" — in his righteousness (i.e., his humility). Even though he was appointed to be the leader of the congregation, he remained "Hoshea" in his righteousness. Similarly, (Shemoth 1:5) "And Yosef was in Egypt." Do we not know that Yosef was in Egypt? — The intent is to apprise us of Yosef's righteousness. (Bereshith 37:2) "Yosef … grazed the sheep with his brothers," and even though he became a king in Egypt, he remained in his (original) righteousness. Similarly, (I Samuel 17:14) "and David was the smallest (i.e., the youngest)." Do we not know that David was the youngest? — The intent is to apprise us of David's righteousness. (I Samuel 16:11) (David was) "tending the sheep" of his father, and even though he became the king of Israel, he remained "David" in his smallness.