2 Samuel 18:25

If he be alone. In case of defeat there would have been a crowd of runaways in eager flight. And when soon afterwards a second courier is seen, as he also is alone, and comes by a different route, his appearance only suggests the idea of completer tidings. And quickly the foremost is recognized by his running as the son of the high priest, and David is then assured that all has gone well, because Joab would not have sent a man of such rank to be the bearer of bad news. The word good may also mean that Ahimaaz was too brave a man to have fled from the battle, and must, therefore, have come on an errand from Joab.