The Pharisees claimed that the traditions of their elders safeguarded the law, but in fact it contravened the law Moses had given. By saying: “Your merchants mix water with the wine,” Isaiah shows that the elders mixed their watery tradition with God’s strict commandment.
In other words, they enjoined an adulterated law which went against the law, as the Lord also made clear when he asked them: “Why do you transgress God’s commandment for the sake of your tradition?”
Their desire to justify these traditions kept them from submitting to God’s law that taught them about the coming of Christ. Instead, they even found fault with the Lord for healing on the sabbath, which was not forbidden by the law, for in a sense the law itself healed by causing circumcision to be performed on the sabbath.
On the other hand, they found no fault with themselves for breaking God’s commandment by their tradition and the Pharisaic law just mentioned, or for lacking the essence of the law, which is love for God.
That this is the first and greatest commandment, the second being love of our neighbor, the Lord taught by saying that the whole of the law and the prophets depend on these two commandments.
He himself brought no greater commandment than this, but he renewed this same commandment by bidding his disciples love God with their whole heart, and their neighbor as themselves.
Paul also says that “love is the fulfillment of the law.” When all other charisms fail, faith, hope, and love remain, but the greatest of all is love. Knowledge is of no avail without the love of God, nor is understanding of mysteries, faith, or prophecy. Without love all are vain and profitless.
Love on the other hand perfects a person and one who loves God is perfect both in this world and the next, for we shall never stop loving God—the longer we gaze upon him the more our love for him will grow.
Against Heresies IV, 12, 2-2: SC 100, 508-14)
Irenaeus (c. 140-200), who was born in Asia Minor and was in his youth a disciple of Saint Polycarp, became bishop of Lyons. Irenaeus wrote his principal work, Against the Heresies, to combat Gnostic dualism. At the heart of his theology is a vision of the unity, the recapitulation of all things in Christ. Just as all have sinned in one man, Adam, so all are offered salvation in Christ, the second Adam.