It’s not often recognized that morality is the basis of the practice of loving-kindness. It’s easier to entertain thoughts of non-ill will when not subject to remorse for transgressions:
This is what should be done
By one who is skilled in goodness,
And who knows the path of peace:
Let them be able and upright,
Straightforward and gentle in speech,
Humble and not conceited,
Contented and easily satisfied,
Unburdened with duties and frugal in their ways.
Peaceful and calm and wise and skillful,
Not proud or demanding in nature.
Let them not do the slightest thing
That the wise would later reprove.—Sn 1.8
"Buddhist ethics is twofold: fulfillment of certain virtues (caritta), and precepts of abstinence (varitta). Caritta, as found in the Metta Sutta, is as follows:
[He] Should be able, honest and upright,
Gentle in speech, meek and not proud.
Contented, he ought to be easy to support,
Not over-busy, and simple in living.
Tranquil his senses, let him be prudent,
And not brazen, nor fawning on families.
Varitta is covered by the next gatha:
Also, he must refrain from any action
That gives the wise reason to reprove him.
Caritta and varitta are thus practiced through metta expressed in bodily and verbal action; the resultant inner happiness and altruistic urge is reflected by the aspirant’s metta of mental action, as found in the conclusion of the stanza:
May all be well and secure,
May all beings be happy!"—Buddharakkhita
“Given that I have declared, Ananda, that good bodily conduct, good verbal conduct, & good mental conduct should be done, these are the rewards one can expect when doing what should be done: One doesn’t fault oneself; observant people, on close examination, praise one; one’s good reputation gets spread about; one dies unconfused; and — on the break-up of the body, after death — one reappears in the good destinations, in the heavenly world. Given that I have declared, Ananda, that good bodily conduct, good verbal conduct, & good mental conduct should be done, these are the rewards one can expect when doing what should be done.”—AN 2.18