When reading “1 Kingdoms” (the Septuagint title for what is popularly known as 1 Samuel) one may notice a wide divergence between the LXX and Masoretic manuscript traditions in the re-telling of the story of David and Goliath.
Both traditions are pretty much the same for the first 11 verses in chapter 17. After that point, the Masoretic recounting of the events requires an additional 19 verses.
What the LXX is missing is a drawn out episode about David being a shepherd for his father Jesse, bringing food to his brothers in the battlefield, over-hearing the boasting of Goliath, and then finally seemingly meeting King Saul the first time (see 1 Sam 17:55-58)–something that directly contradicts the end of chapter 16 as David was already known to Saul, played music for him, and was employed as his armor bearer.
What I found interesting was this–if we cut out everything between verses 12 and 31 (as the LXX presents the episode) the story actually makes more sense. David, as Saul’s armor bearer, is nearby and can assure him that he can fight Goliath. The story flows smoothly and without seeming contradiction. (The Masoretic text also goes into more detail about David trying on Saul’s armor and his approaching of Goliath.)
It is unknown whether the Masoretic Text or the Septuagint includes the earlier rendering of the David and Goliath story. Textual critics obviously prefer the MT, as they view Biblical contradictions as proof of the “development” of 1 Samuel through the melding of editors and different sources. However, the limited Dead Sea Scroll manuscript evidence we have more often than not accords with the LXX when it and the MT diverge–this includes 1 Sam 17.