Thomas Aquinas,
Summa Theologiae — Question 90 - OF THE FORM OF THE JUDGE IN COMING TO THE JUDGMENT…
“ But the goods of the Creation would not suffice us to obtain the reward of eternal life, without the addition of the boon of the Redemption, on account of the obstacle accruing to created nature through the sin of our first parent. Hence, since the last judgment is directed to the admission of some to the kingdom, and the exclusion of others therefrom, it is becoming that Christ should preside at that judgment under the form of His human nature, since it is by favor of that same nature's Redemption that man is admitted to the kingdom. ”
