'Reward' in the Bible

when a man told me, ‘Behold, Saul is dead,’ thinking that he was bringing good news, I seized and killed him in Ziklag, to reward him for his news.

Then Ahimaaz the son of Zadok said again to Joab, “But whatever happens, please let me also run after the Cushite.” Joab said, “Why should you run, my son, seeing you will have no messenger’s reward for going [because you have only bad news]?”

Your servant would merely cross over the Jordan with the king. Why should the king compensate me with this reward?