Rashi on I Samuel
A champion. A mighty person who went out from his battalion, to stand between the two battalions.2Following the literal meaning of אִישׁ הַבֵּנַיִם as ‘the man of between.’ However, Maseches Sotah 42b states that the word הַבֵּנַיִם is from the root בנה, to build, i.e., he was as sturdy as a building.—Da’as Sofrim