Is Abraham in Heaven and How Did He Achieve His Divine Nature?
According to The Catechism of Pope Pius X, the souls of the holy Fathers were not admitted into heaven before the death of Jesus Christ, because heaven was closed by the sin of Adam, and it was but fitting that Jesus Christ, who reopened it by His death, should be the first to enter it.
This teaching can be further explained in the Catechism of the Catholic Church as it addresses Article Five of the Apostles' Creed (631-637), which states:
"He descended into hell on the third day he rose again.""This 'hell' was different from the hell of the damned. It was the state of all those, righteous and evil, who died before Christ. With his soul united to his divine Person Jesus went down to the just in hell who were awaiting their Redeemer so they could enter at last into the vision of God. When he had conquered by his death both death and the devil 'who has the power of death' (Hebrews 2:14), he freed the just who looked forward to the Redeemer and opened for them the gates of Heaven." (Compendium: Catechism of the Catholic Church (CCC), USCCB 2006) (See CCC 635)
The Church refers to this state as Limbo: (Late Lat. limbus) a word of Teutonic derivation, meaning literally "hem" or "border," as of a garment, or anything joined on (cf. Italian lembo or English limb).
In theological usage the name is applied to (a) the temporary place or state of the souls of the just who, although purified from sin, were excluded from the beatific vision until Christ's triumphant ascension into Heaven (the "limbus patrum"); or (b) to the permanent place or state of those unbaptized children and others who, dying without grievous personal sin, are excluded from the beatific vision on account of original sin alone (the "limbus infantium" or "puerorum"). Taken from the New Advent dictionary.
* This latter definition dealing with children who die without Baptism, has come into question recently as the Vatican has assigned an International Commission of Catholic Theologians to review this teaching from the 13 century. Limbo has never been a defined dogma of the Church, but is instead a concept worked out by theologians as a way to try to solve a conflict between the necessity of Baptism and the mercy of God. In view of that, the Catechism of the Catholic Church states, "As regards children who have died without Baptism, the Church can only entrust them to the mercy of God...In fact the great mercy of God, who wants all men to be saved, and the tenderness of Jesus towards children... allow us to hope that there is a way of salvation for children who die without baptism." (CCC, Article 1261)