34 But perhaps you think your impiety has still an opportunity left to see in the words, Father, into Your hands I commend My Spirit, a proof that He feared the descent into the lower world, and even the necessity of death. But when you read these words and could not understand them, would it not have been better to say nothing, or to pray devoutly to be shown their meaning, than to go astray with such barefaced assertions, too mad with your own folly to perceive the truth?
Could you believe that He feared the depths of the abyss, the scorching flames, or the pit of avenging punishment, when you listen to His words to the thief on the cross, Verily, I say unto you, Today shall you be with Me in Paradise ? Such a nature with such power could not be shut up within the confines of the nether world, nor even subjected to fear of it. When He descended to Hades, He was never absent from Paradise (just as He was always in Heaven when He was preaching on earth as the Son of Man), but promised His martyr a home there, and held out to him the transports of perfect happiness.
Bodily fear cannot touch Him Who reaches indeed down as far as Hades, but by the power of His nature is present in all things everywhere. As little can the abyss of Hell and the terrors of death lay hold upon the nature which rules the world, boundless in the freedom of its spiritual power, confident of the raptures of Paradise; for the Lord Who was to descend to Hades, was also to dwell in Paradise. Separate, if you can, from His indivisible nature a part which could fear punishment: send the one part of Christ to Hades to suffer pain, the other, you must leave in Paradise to reign: for the thief says, Remember me when You come in Your Kingdom.
It was the groan he heard, I suppose, when the nails pierced the hands of our Lord, which provoked in him this blessed confession of faith: he learned the Kingdom of Christ from His weakened and stricken body! He begs that Christ will remember him when He comes in His Kingdom: you say that Christ feared as He hung dying upon the cross. The Lord promises him, Today shall you be with Me in Paradise; you would subject Christ to Hades and fear of punishment. Your faith has the opposite expectation. The thief confessed Christ in His Kingdom as He hung on the cross, and was rewarded with Paradise from the cross: you who impute to Christ the pain of punishment and the fear of death, will fail of Paradise and His Kingdom.
Source: On the Trinity (New Advent)