Objection 1. It would seem that Christ descending into hell did not deliver the holy Fathers from thence. For Augustine (Epist. ad Evod. clxiv) says: "I have not yet discovered what Christ descending into hell bestowed upon those righteous ones who were in Abraham's bosom, from whom I fail to see that He ever departed according to the beatific presence of His Godhead." But had He delivered them, He would have bestowed much upon them. Therefore it does not appear that Christ delivered the holy Fathers from hell.
Objection 2. Further, no one is detained in hell except on account of sin. But during life the holy Fathers were justified from sin through faith in Christ. Consequently they did not need to be delivered from hell on Christ's descent thither.
Objection 3. Further, if you remove the cause, you remove the effect. But that Christ went down into hell was due to sin which was taken away by the Passion, as stated above (Question 49, Article 1). Consequently, the holy Fathers were not delivered on Christ's descent into hell.
On the contrary, Augustine says in the sermon on the Passion already quoted that when Christ descended into hell "He broke down the gate and 'iron bars' of hell, setting at liberty all the righteous who were held fast through original sin."
I answer that, As stated above (4, ad 2), when Christ descended into hell He worked through the power of His Passion. But through Christ's Passion the human race was delivered not only from sin, but also from the debt of its penalty, as stated above (49, 1,3). Now men were held fast by the debt of punishment in two ways: first of all for actual sin which each had committed personally: secondly, for the sin of the whole human race, which each one in his origin contracts from our first parent, as stated in Romans 5 of which sin the penalty is the death of the body as well as exclusion from glory, as is evident from Genesis 2 and 3: because God cast out man from paradise after sin, having beforehand threatened him with death should he sin. Consequently, when Christ descended into hell, by the power of His Passion He delivered the saints from the penalty whereby they were excluded from the life of glory, so as to be unable to see God in His Essence, wherein man's beatitude lies, as stated in the I-II, 3, 8. But the holy Fathers were detained in hell for the reason, that, owing to our first parent's sin, the approach to the life of glory was not opened. And so when Christ descended into hell He delivered the holy Fathers from thence. And this is what is written Zechariah 9:11: "Thou also by the blood of Thy testament hast sent forth Thy prisoners out of the pit, wherein is no water." And (Colossians 2:15) it is written that "despoiling the principalities and powers," i.e. "of hell, by taking out Isaac and Jacob, and the other just souls," "He led them," i.e. "He brought them far from this kingdom of darkness into heaven," as the gloss explains.
Reply to Objection 1. Augustine is speaking there against such as maintained that the righteous of old were subject to penal sufferings before Christ's descent into hell. Hence shortly before the passage quoted he says: "Some add that this benefit was also bestowed upon the saints of old, that on the Lord's coming into hell they were freed from their sufferings. But I fail to see how Abraham, into whose bosom the poor man was received, was ever in such sufferings." Consequently, when he afterwards adds that "he had not yet discovered what Christ's descent into hell had brought to the righteous of old," this must be understood as to their being freed from penal sufferings. Yet Christ bestowed something upon them as to their attaining glory: and in consequence He dispelled the suffering which they endured through their glory being delayed: still they had great joy from the very hope thereof, according to John 8:56: "Abraham your father rejoiced that he might see my day." And therefore he adds: "I fail to see that He ever departed, according to the beatific presence of His Godhead," that is, inasmuch as even before Christ's coming they were happy in hope, although not yet fully happy in fact.
Reply to Objection 2. The holy Fathers while yet living were delivered from original as well as actual sin through faith in Christ; also from the penalty of actual sins, but not from the penalty of original sin, whereby they were excluded from glory, since the price of man's redemption was not yet paid: just as the faithful are now delivered by baptism from the penalty of actual sins, and from the penalty of original sin as to exclusion from glory, yet still remain bound by the penalty of original sin as to the necessity of dying in the body because they are renewed in the spirit, but not yet in the flesh, according to Romans 8:10: "The body indeed is dead, because of sin; but the spirit liveth, because of justification."
Reply to Objection 3. Directly Christ died His soul went down into hell, and bestowed the fruits of His Passion on the saints detained there; although they did not go out as long as Christ remained in hell, because His presence was part of the fulness of their glory.
Source: Summa Theologica (New Advent)