The Moral Reflections on Job by Pope St Gregory the Great

The law of the Lord is manifold

If only God would show you how manifold is his law. How must we interpret this law of God? How, if not by love? The love that stamps the precepts of right-living on the mind and bids us put them into practice. Listen to Truth speaking of this law: This is my commandment, that you love one another. Listen to Paul: The whole law, he declares, is summed up in love; and again: Help one another in your troubles, and you will fulfil the law of Christ. The law of Christ – does anything other than love more fittingly describe it? Truly we are keeping this law when, out of love, we go to the help of a brother in trouble.
But we are told that this law is manifold. Why? Because love’s lively concern for others is reflected in all the virtues. It begins with two commands, but it soon embraces many more. Paul gives a good summary of its various aspects. Love is patient, he says, and kind; it is never jealous or conceited; its conduct is blameless; it is not ambitious, not selfish, not quick to take offence; it harbours no evil thoughts, does not gloat over other people’s sins, but is gladdened by an upright life.
The man ruled by this love shows his patience by bearing wrongs with equanimity; his kindness by generously repaying good for evil. Jealousy is foreign to him. It is impossible to envy worldly success when he has no worldly desires. He is not conceited. The prizes he covets lie within; outward blessings do not elate him. His conduct is blameless, for he cannot do wrong in devoting himself entirely to love of God and his neighbour. He is not ambitious. The welfare of his own soul is what he cares about. Apart from that he seeks nothing. He is not selfish. Unable to keep anything he has in this world, he is as indifferent to it as if it were another’s. Indeed, in his eyes nothing is his own but what will be so always. He is not quick to take offence. Even under provocation, thought of revenge never crosses his mind. The reward he seeks hereafter will be greater in proportion to his endurance. He harbours no evil thoughts. Hatred is utterly rooted out of a heart whose only love is goodness. Thoughts that defile a man can find no entry. He does not gloat over other people’s sins. No; an enemy’s fall affords him no delight, for loving all men, he longs for their salvation.
On the other hand, he is gladdened by an upright life. Since he loves others as himself, he takes as much pleasure in whatever good he sees in them as if the progress were his own. That is why this law of God is manifold.