How old was David when he fought Goliath?
1 Samuel 17:33 (NRSV) says:
Saul said to David, “You are not able to go against this Philistine to fight with him; for you are just a boy, and he has been a warrior from his youth.”
I have taken into consideration the answer stated in this link, which argues that David was 15 years old or younger. Are there any proven claims on the exact age of David when he fought Goliath? If not, what is the best approximation?
Thanks for you first question on BH.SE. Two things: (1) You should add a specific verse quote/reference into your question, since one of the requirements for this site is to have a specific text at least as a start point for the question (perhaps 1 Sam 17:33). (2) Do not expect a "proven" claim on "exact age," because if such existed, there would not be all the controversy about how old he was. However, you may get some answers that give even more biblical evidence to pinpoint a _good approximation_ of age for David.
Welcome to Biblical Hermeneutics Stack Exchange! Be sure to take our site tour to learn more about us. We're a little different from other sites. Be sure to properly cite the text you're asking about. The chapter and verse numbers do not always line up between the Hebrew, Greek, and English texts. I've edited your post in line with ScottS's helpful comment. I also added the claim from the link into the question, as Internet links change.
The only Biblical answer I can find is that the men were at least 20 to be in the army. So David would have been less then twenty if he was considered too young to fight.
from twenty years old and upward, whoever is able to go out to war in Israel, you and Aaron shall number them by their armies.
The following is only conjecture and can not be proved, though I do think it is logical.
Based on the age (of twenty) of "manhood" and a few more references (to show my work), it is possible to make a logical guess.
1) We know that his 3 oldest brothers were at the fight.
Now David was the son of the Ephrathite of Bethlehem in Judah, whose name was Jesse, and he had eight sons. And Jesse was old in the days of Saul, advanced in years among men. The three older sons of Jesse had gone after Saul to the battle. And the names of his three sons who went to the battle were Eliab the firstborn, and the second to him Abinadab, and the third Shammah.
2) Assuming that all who were old enough to go to war went.
Now the war against the Philistines was severe all the days of Saul; and when Saul saw any mighty man or any valiant man, he attached him to his staff.
3) And if Shammah, the youngest of the 3 that went, was 20 then that leaves 4 brothers between them and David. If they were born a year apart then David would be 14 or 15. Obviously if they were born with more time between them then David could be even younger.
If not all were required to join the war but only those that wanted to, then David could be up to 19.
It is worth noting that both the Hebrews and Goliath thought David was a boy that was too young to fight. So if he was 19 then he might not have really looked like a boy.
Based on this line of reasoning, I think he was between 12 and 15 years old when he fought and killed Goliath, though nothing is certain.
@PaulVargas, I have made another update. Is this better or do I still need more?