Envying a friend
Envy appears in the suttas by name and with a specific instruction: it is let go of by looking at it wisely, again and again, not by scolding or by saying the right thing. The other half of the answer is the practice of gladness at another's good, taught alongside love and compassion as one of the boundless states. The passages here look at what the comparing does to the one comparing, and at how a boundless heart begins with one person. They do not ask you to want less for yourself.
What the suttas say
Nasty jealousy should be given up neither by the body, nor by speech, but by seeing again and again with wisdom.
Envy is treated as something to be seen through, not suppressed or confessed away.
Where this stops: The examples are of a servant envying a householder and a monk envying another's requisites; carry the method, not the social setting.
AN 10.23:5.1 · Body
Pāpikā, bhikkhave, issā neva kāyena pahātabbā no vācāya, paññāya disvā pahātabbā.
Even as a mother would protect with her life her child, her only child, so too for all creatures unfold a boundless heart. With love for the whole world, unfold a boundless heart: above, below, all round, unconstricted, without enmity or foe. When standing, walking, sitting, or lying down while yet unweary, keep this ever in mind; for this, they say, is a divine meditation in this life.
The Metta Sutta's central image, in the canon's own words.
Where this stops: The verses are an ideal of the practitioner; the opening lines describing a skilled and honest person are a description, not a prerequisite for beginning. Never use it to quiet anger that has something to say, and never present it as a recitation that protects anyone. The mother guarding her only child is not for someone after a pregnancy loss.
Kp 9:7.1–9.4 · The Discourse on Love
Mātā yathā niyaṁ puttam Āyusā ekaputtamanurakkhe; Evampi sabbabhūtesu, Mānasaṁ bhāvaye aparimāṇaṁ. Mettañca sabbalokasmi, Mānasaṁ bhāvaye aparimāṇaṁ; Uddhaṁ adho ca tiriyañca, Asambādhaṁ averamasapattaṁ. Tiṭṭhaṁ caraṁ nisinno va, Sayāno yāvatāssa vitamiddho; Etaṁ satiṁ adhiṭṭheyya, Brahmametaṁ vihāramidhamāhu.
They meditate spreading a heart full of rejoicing to one direction, and to the second, and to the third, and to the fourth. In the same way above, below, across, everywhere, all around, they spread a heart full of rejoicing to the whole world—abundant, expansive, limitless, free of enmity and ill will.
Rejoicing in others' good is one of the four boundless states, taught to the Kālāmas in the same breath as love — the canon's own answer to envy.
Where this stops: The formula is generic to the four states; use it for the practice of gladness, not as a claim that the Kālāma discourse is about envy.
AN 3.65:42.3 · With the Kālāmas of Kesamutta
muditāsahagatena cetasā …pe…
We will meditate spreading a heart of love to that individual. And with them as a basis, we will meditate spreading a heart full of love to everyone in the world—abundant, expansive, limitless, free of enmity and ill will.’
Mettā starts with the specific person who spoke harshly, then widens; the order matters.
Where this stops: A training for one's own mind under hard speech. It is never a reason to stay where someone keeps speaking to you with contempt or threats, and never a ruling on whether to leave.
MN 21:11.14 · The Simile of the Saw
Tañca puggalaṁ mettāsahagatena cetasā pharitvā viharissāma, tadārammaṇañca sabbāvantaṁ lokaṁ mettāsahagatena cittena vipulena mahaggatena appamāṇena averena abyābajjhena pharitvā viharissāmā’ti.
“Mendicants, you can expect eleven benefits when the heart’s release by love has been cultivated, developed, and practiced, made a vehicle and a basis, kept up, consolidated, and properly implemented. What eleven? You sleep at ease. You wake happily. You don’t have bad dreams. Humans love you. Non-humans love you. Deities protect you. You can’t be harmed by fire, poison, or blade. Your mind quickly enters immersion. Your face is clear and bright. You don’t feel lost when you die. If you don’t penetrate any higher, you’ll be reborn in a realm of divinity. You can expect eleven benefits when the heart’s release by love has been cultivated, developed, and practiced, made a vehicle and a basis, kept up, consolidated, and properly implemented.”
The plain, this-life benefits — sleep, dreams, a clear face — for someone who thinks mettā is sentimental.
Where this stops: The benefits are tied to love developed into a release of the heart, not occasional well-wishing. Protection from fire, poison and weapons, guarding deities and divine rebirth are the sutta's claims; never present them as safety or outcome promises.
AN 11.15:1.1–2.4 · The Benefits of Love
“Mettāya, bhikkhave, cetovimuttiyā āsevitāya bhāvitāya bahulīkatāya yānīkatāya vatthukatāya anuṭṭhitāya paricitāya susamāraddhāya ekādasānisaṁsā pāṭikaṅkhā. Katame ekādasa? Sukhaṁ supati, sukhaṁ paṭibujjhati, na pāpakaṁ supinaṁ passati, manussānaṁ piyo hoti, amanussānaṁ piyo hoti, devatā rakkhanti, nāssa aggi vā visaṁ vā satthaṁ vā kamati, tuvaṭaṁ cittaṁ samādhiyati, mukhavaṇṇo vippasīdati, asammūḷho kālaṁ karoti, uttari appaṭivijjhanto brahmalokūpago hoti. Mettāya, bhikkhave, cetovimuttiyā āsevitāya bhāvitāya bahulīkatāya yānīkatāya vatthukatāya anuṭṭhitāya paricitāya susamāraddhāya ime ekādasānisaṁsā pāṭikaṅkhā”ti. Pañcamaṁ.