David’s general Joab was a ruthless sort of guy.  On the plus side, he was loyal to his king when many deserted him to follow Absalom (2 Samuel  15-18).  He also rebuked David twice when his decisions were questionable (2 Samuel 19.5-7 and 24.3).

But he was vengeful, murdering Israel’s general Abner, who had killed Joab’s brother during an earlier battle (2 Samuel 3.26-27).  He also murdered David’s son Absalom (2Samuel 18.9-15). He was deceitful, prompting an old woman with a fictitious story to manipulate the king (2 Samuel 14). 

So, the otherwise hugely heroic line from 2 Samuel 10.12 seems a bit tainted.  Joab and his men are outnumbered and caught between Syrian and Ammonite forces.  He deploys his men strategically, draws out a simple battle plan, then encourages his men and proclaims his trust in God with “Be of good courage, and let us be courageous for our people, and for the cities of our God, and may the LORD do what seems good to him.”  Because of Joab’s other actions, you wonder if he is being sincere or fatalistic.

God wins the battle for the Israelites.   And maybe that is the point – God does the winning.  Characters in the Bible are shown with all their flaws – vengeful, deceitful, adulterous, murdering offenders against God’s holiness.  But God has a wonderful plan for his creation, saving those who believe in Him and allowing men to be heroic at times even though they are sinners.