Taken from the Catholic website, http://www.catholic.com, under the heading “Roots of Purgatory”:
All Christians agree that we won’t be sinning in heaven. Sin and final glorification are utterly incompatible. Therefore, between the sinfulness of this life and the glories of heaven, we must be made pure. Between death and glory there is a purification.
Thus, the Catechism of the Catholic Church states: “All who die in God’s grace and friendship, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven. The Church gives the name purgatory to this final purification of the elect, which is entirely different from the punishment of the damned” (Catechism of the Catholic Church, articles #1030–1).
This is in direct contradiction to many passages of Scripture, such as 1 John 1:7: “but if we walk in the Light as He Himself is in the Light, we have fellowship with one another, and the blood of Jesus His Son cleanses us from all sin.” His blood cleanses those who believe from how much sin? ALL SIN; therefore there is no further cleansing (or purification) needed.