וַיֹּ֨אמֶר שָׁא֜וּל אֶל־דָּוִ֗ד לֹ֤א תוּכַל֙ לָלֶ֙כֶת֙ אֶל־הַפְּלִשְׁתִּ֣י הַזֶּ֔ה לְהִלָּחֵ֖ם עִמּ֑וֹ כִּֽי־נַ֣עַר אַ֔תָּה וְה֛וּא אִ֥ישׁ מִלְחָמָ֖ה מִנְּעֻרָֽיו׃ (ס)
掃羅對大衛說：«你不能去與這非利士人交戰，因為你還年輕，他卻自幼就是戰士。»
Kitzur Ba'al HaTurim
מנעריו From the youth in 3 different places in Tanakh teaches "a man of war from his youth (I Sam. 17:33)." "Mo᾽av has been at ease from his youth (Jer 48:11)." From his youth, a man must fight with the evil inclination and if he overcomes him and his victory is that he is Moab from his youth, "and he has settled on his lees (Jer 48:11)."