Jamieson, Fausset and Brown on 1 Chronicles 11:15-19

15-19. David longed, and said, Oh that one would give me drink ... of the well of Beth-lehem--(See on 2Sa 23:15). This chivalrous act evinces the enthusiastic devotion of David's men, that they were ready to gratify his smallest wish at the risk of their lives. It is probable that, when uttering the wish, David had no recollection of the military posted at Beth-lehem. It is generally taken for granted that those who fought a way to the well of Beth-lehem were the three champions just mentioned [see on 1Ch 11:13]. But this is far from being clear. On the contrary, it would seem that three different heroes are referred to, for Abishai (1Ch 11:20) was one of them. The camp of the Philistines was in the valley of Rephaim (1Ch 11:15), which lay on the west of Jerusalem, but an outpost was stationed at Beth-lehem (1Ch 11:16), and through this garrison they had to force a passage.