And Saul said to David: Thou art not able to withstand this Philistine, nor to fight against him: for thou art but a boy, but he is a warrior from his youth.

And Saul saith unto David, 'Thou art not able to go unto this Philistine, to fight with him, for a youth thou art, and he a man of war from his youth.'

And Saul said to David, You are not able to go out against this Philistine and have a fight with him: for you are only a boy, and he has been a man of war from his earliest days.

And Saul said to David: "You are not able to withstand this Philistine, nor to fight against him. For you are a boy, but he has been a warrior from his boyhood."

Thou art but a youth - Supposed to be about twenty-two or twenty-three years of age.

And Saul said to David, Thou art not (k) able to go against this Philistine to fight with him: for thou [art but] a youth, and he a man of war from his youth.
(k) Here Satan proves David's faith, by the infidelity of Saul.

And Saul said to David, thou art not able to go against this Philistine to fight with him,.... Had neither strength of body, nor skill in military affairs, to encounter with a man of his stature, and warlike genius and practice:
for thou art but a youth; some say about fourteen or sixteen years of age, but very probably about twenty, and not more, and so not only weak, but inexpert in the art of fighting:
and he a man of war from his youth; a gigantic man, trained up in, inured to, and expert in the affairs of war; so that David could not, on any account, be a competitor with him, and a match for him.

A youth - Not above 20 years old; and a novice, a raw and unexperienced soldier.