In the Roman arena, the defeated gladiator was usually killed by the victor. The loser’s only hope was that the emperor, as he watched from his rostrum, would give him the “thumbs up.” This was the sign that he was to be spared as an act of imperial favor.
If we picture ourselves as a vanquished gladiator thrown to the ground, with our opponent’s sword poised over our neck, and if we imagine looking up in our despair and seeing against all hope that imperial “thumbs up,” we may begin to understand the meaning of God’s mercy.
Now reverse the image – you stand over the loser and your sword is at his throat. If it were up to you, would your thumb go up or down? The best assessment of your grasp of God’s mercy is shown by your own mercy.