When the Lord Jesus was teaching the crowds, he did not fail to confirm the law which the Creator had inscribed on men’s hearts and had then formulated on the tablets of the Decalogue. “Think not that I have come to abolish the law and the prophets; I have come not to abolish them but to fulfil them. For truly, I say to you, till heaven and earth pass away, not an iota, not a dot, will pass from the law until all is accomplished” (Mt 5:17-18). But Jesus showed us with a new clarity the unifying centre of the divine laws revealed on Sinai, namely love of God and love of neighbour: “To love [God] with all the heart, and with all the understanding, and with all the strength, and to love one’s neighbour as oneself, is much more than all whole burnt offerings and sacrifices” (Mk 12:33). Indeed, in his life and in his Paschal Mystery Jesus brought the entire law to completion. Uniting himself with us through the gift of the Holy Spirit, he carries with us and in us the “yoke” of the law, which thereby becomes a “light burden” (Mt 11:30). In this spirit, Jesus formulated his list of the inner qualities of those who seek to live their faith deeply: Blessed are the poor in spirit, those who weep, the meek, those who hunger and thirst for justice, the merciful, the pure in heart, the peacemakers, those who are persecuted for righteousness’ sake ... (cf. Mt 5:3-12).
[Pope Benedict, homily Warsaw 26 May 2006]