VI. The Sacrament of Penance and Reconciliation

1447
Over
the centuries the concrete form in which the Church has exercised this power
received from the Lord has varied considerably. During the first centuries the
reconciliation of Christians who had committed particularly grave sins after
their Baptism (for example, idolatry, murder, or adultery) was tied to a very
rigorous discipline, according to which penitents had to do public penance for
their sins, often for years, before receiving reconciliation. To this
“order of penitents” (which concerned only certain grave sins), one
was only rarely admitted and in certain regions only once in a lifetime. During
the seventh century Irish missionaries, inspired by the Eastern monastic
tradition, took to continental Europe the “private” practice of
penance, which does not require public and prolonged completion of penitential
works before reconciliation with the Church. From that time on, the sacrament
has been performed in secret between penitent and priest. This new practice
envisioned the possibility of repetition and so opened the way to a regular
frequenting of this sacrament. It allowed the forgiveness of grave sins and
venial sins to be integrated into one sacramental celebration. In its main
lines this is the form of penance that the Church has practiced down to our
day.

From The Catechism of the Catholic Church – rosary.team

Original Link: https://www.vatican.va/archive/ENG0015/__P4C.HTM