The Sacraments Explained: According to Teaching and Doctrine of Catholic Church

Since the foundation of Christianity and the institution
of the Church we are living under the guidance of the Holy
Spirit Whom Christ promised to send, and Who descended
on the Apostles and disciples on the Day of Pentecost.
Our Lord, before departing out of this world to His Father,
taught and clearly indicated the form of His future dealings
with human souls, which was to be Sacramental in character.
What He personally did when living amongst men by the
touch of His hand, or by breathing on them, He has
continued to do in His Church by His Sacraments,
making them the vehicles for imparting His life to our
souls.