4 But further, attend, I pray, to the very principle of justice, and come to your own case. You have different sorts of servants: and some are good and some bad; you honour therefore the good, and smitest the bad. And if you are a judge, to the good you award praise, and to the transgressors, punishment. Is then justice observed by you a mortal man; and with God, the ever changeless King of all, is there no retributive justice? Nay, to deny it is impious. For consider what I say.
Many murderers have died in their beds unpunished; where then is the righteousness of God? Yea, ofttimes a murderer guilty of fifty murders is beheaded once; where then shall he suffer punishment for the forty and nine? Unless there is a judgment and a retribution after this world, you charge God with unrighteousness. Marvel not, however, because of the delay of the judgment; no combatant is crowned or disgraced, till the contest is over; and no president of the games ever crowns men while yet striving, but he waits till all the combatants are finished, that then deciding between them he may dispense the prizes and the chaplets. Even thus God also, so long as the strife in this world lasts, succours the just but partially, but afterwards He renders to them their rewards fully.
Source: Catechetical Lectures (New Advent)