But Abishai the son of Zeruiah aided him, and struck the Philistine, and killed him. Then the men of David swore unto him, saying, You shall go no more out with us to battle, that you quench not the light of Israel.
All Commentaries on 2 Samuel 21:17 Go To 2 Samuel 21
Augustine of Hippo
AD 430
At this point someone may say that the priests of God ought to flee from such threatening dangers in order to save themselves for the service of the church in more peaceful times. It is right for some to do this when others are not lacking to supply the ministry of the church, so that it is not wholly abandoned. This is what Athanasius did, as I said before; for the body of Catholic believers knew how necessary and how profitable it was for the church to retain in the flesh a man who had defended it by words and heart’s love against the Arian heretics. But when the danger is common to all and there is more reason to fear that the priest’s escape may be attributed to a dread of death rather than an intention of future help, and when he does more harm by the example of his flight than he would do good by his preservation, there is no justifiable reason for doing it. Finally, there was holy David, who did not trust himself to the dangers of battle lest the lamp of Israel, as it is there said, “should be put out”; but he did not take this course himself—he did it because his followers begged him to do it. Otherwise, he would have had many cowardly imitators who would believe that he acted thus at the bidding of his own fear, not for any motive of usefulness to others.