Benaiah son of Jehoiada holds a unique position within the hierarchy of David's military elite. His extraordinary acts of bravery earned him a famous reputation among a specific trio of warriors known for retrieving water for the king.
The primary approach among commentators [מצודת דוד, רלב״ג, אברבנאל] is that Benaiah belonged to a second trio of elite fighters who commanded a larger group of thirty warriors. His rank reflects a middle ground. On one hand, he was honored far above the standard thirty, preventing him from being counted as a regular soldier among them, and his peers within the trio held him in high regard. On the other hand, despite his immense courage, he did not quite reach the supreme standing of the first, highest-ranking trio of warriors.
A notable detail emerges regarding the makeup of this second trio. Out of the three, only Abishai and Benaiah are highlighted, as both built a strong reputation through additional independent acts of bravery. The third member of the group remains unnamed in this context. [אברבנאל] suggests that this third fighter may have been of a lower rank, perhaps simply joining Abishai and Benaiah for the specific water retrieval mission without having his own record of notable solo exploits. Alternatively, [אברבנאל] proposes that this anonymous third hero is Adina son of Shiza the Reubenite, a figure identified in the Book of Chronicles as a leader over a group of thirty warriors.