Deuteronomy 6:6

Then I returned answer, “You perceive that God by Moses laid all such ordinances upon you on account of the hardness of your people’s hearts, in order that, by the large number of them, you might keep God continually, and in every action, before your eyes, and never begin to act unjustly or impiously. For He enjoined you to place around you [a fringe] of purple dye, in order that you might not forget God; and He commanded you to wear a phylactery, certain characters, which indeed we consider holy, being engraved on very thin parchment; and by these means stirring you up to retain a constant remembrance of God: at the same time, however, convincing you, that in your hearts you have not even a faint remembrance of God’s worship. …

XXIII . For He did not take away the law of nature, but confirmed it. For He that said in the law, “The Lord thy God is one Lord;” the same says in the Gospel, “That they might know Thee, the only true God.” And He that said, “Thou shalt love thy neighbour as thyself,” says in the Gospel, renewing the same precept, “A new commandment I give unto you, that ye love one another.” He who then forbade murder, does now forbid causeless anger. He that forbade adultery, does now forbid all unlawful lust. He that forbade stealing, now pronounces him most happy who supplies those that are in want out of his own labours. He that forbade hatred, now pronounces him blessed that loves his enemies. He that forbade revenge, now commands long-suffering; not as if just revenge were an unrighteous thing, but because long-suffering is more excellent. …