The New testament, which is ordered to eternal life not only through precepts but also through the gifts of grace, is divided into three parts. In the first the origin of grace is treated, in the Gospels. In the second the power of grace, and this in the epistles of Paul, hence he begins in the power of the Gospel, in Romans 1:16 saying, “For I am not ashamed of the Gospel, for it is the power of God unto salvation to everyone who believes.” In the third, the execution of the aforesaid virtues is treated, and this in the rest of the books of the New Testament.
Christ is the origin of grace. John 1:16-17: “And of his fullness we have all received, grace for grace. For the Law was given through Moses: grace and truth came through Jesus Christ.” In Christ a twofold nature is to be considered, a divine, and the Gospel of John is chiefly concerned with this, hence he begins, “In the beginning was the Word and Word was with God, and the Word was God.” And a human, and the other Gospels treat chiefly of this, and they are distinguished according to the threefold dignity that belongs to the man Christ. With respect to his royal honor, Matthew speaks. Hence in the beginning of his Gospel he shows that Christ descended from kings and was adored by the Magi kings. With respect to his prophetic honor, Mark speaks, hence he begins with the preaching of the Gospel. With respect to this priestly dignity, Luke speaks, and he begins with the temple and the priesthood and ends his Gospel in the temple, and frequently returns to the temple, as the Gloss says says about Luke 2:46, “And they found him sitting in the temple in the midst of the teachers.”
In another way, Matthew might be said to speak of Christ chiefly with respect to the mystery of the Incarnation, and thus he is depicted in the figure of a man. Luke with respect to the mystery of the Passion, and therefore he is depicted as a bull, which is in animal to be immolated. Mark, with respect to the victory of the Resurrection, and thus he is depicted as a lion But John, who soars to the heights of His divinity, is depicted as an eagle.
The execution of the power of grace is shown in the progress of the Church, in which there are three things to consider. First, the beginning of the Church, and this is treated in the Acts of the Apostles, hence Jerome says, in his preface to the Pentateuch, that “The Acts of the Apostles seem to give the bare history of the birth and to clothe the infant Church.” Second, the progress of the Church, and to this is ordered the apostolic instruction of the canonical epistles. Third, the end of the Church, with which the whole content of Scripture concludes in the Apocalypse, with the spouse in the abode of Jesus Christ sharing the life of glory, to which Jesus Christ himself conducts, and may he be blessed for ever and ever. Amen.