That David was barely a teenager when he fought Goliath is a Myth,
although he is shown in many illustrations as very young. That comes from the Latin text which calls David a child, a miss-translation of the Hebrew, which calls him a young man.
David was at least twenty-seven, maybe twenty-eight, when he fought Goliath. The key to David’s age is the two years of Saul’s reign and the seven and a half years that David was king over Judah while he was in Hebron. David was thirty when he began his reign in Hebron, which came immediately after Saul’s two-year reign.
(See 1 Samuel 13:1. See Timeline in the Hebrew Texts chapter of the One New Man Bible Companion.)
The One New Man Bible Companion, at 242 pages, with more than two-hundred indexed subjects including: the nature of God, covenant, the Hebrew and Greek languages, religious myths, biblical word meanings, teachings, Jewish roots, the Patriarchs, biblical weights and measures, Hebrew months, map of the united kingdom in the days of David and Solomon is the perfect partner to getting the most out of your One New Man Bible!