In the Book of Samuel, David, the anointed king of Israel, becomes a fugitive when Saul, the king from whom God removed His favor, tries to kill David. We are told that David "was joined by all those in difficulties or in debt, or embittered, and became their leader" (1 Sam 22:2). For a man about to raise a veritable guerrilla army, this does not seem like very promising material. Then again, it sounds much like the "tax collectors and sinners" who appear throughout the Gospels following Jesus.
Interestingly, we learn a few chapters later from some shepherds who traveled through the territory of David and his outlaws that "these men were very good to us. We were not harmed, neither did we miss anything all the while we were living among them during our stay in the open country" (1 Sam 25:15). It turns out that, under a leader like David, the indebted, the embittered, the outcasts of society, can become not only a capable fighting force but upstanding men as well. Thus does the Old Testament foreshadow here, and in dozens of more prominent examples, the idea that St. Paul explained to the Corinthians: "God chose the foolish of the world to shame the wise, and God chose the weak of the world to shame the strong" (1 Cor 1:27).
