CHORUS: I hope the man who does not honour his friends, the man who does not open an honest heart to them, I hope that man dies a horrible, a miserable death. Such a man will certainly never be a friend of mine!

[ΚΥΚΛΩΨ: ἀχάριστος ὄλοιθ᾽ ὅτῳ πάρεστιν
μὴ φίλους τιμᾶν καθαρᾶν ἀνοί-
ξαντα κλῇδα φρενῶν: ἐμοὶ
μὲν φίλος οὔποτ᾽ ἔσται.]

Euripides (485?-406? BC) Greek tragic dramatist
Medea [Μήδεια], l. 659ff, Antistrophe 2 (431 BC) [tr. Theodoridis (2004)]
    (Source)

(Source (Greek)). Other translations:

Perish the wretch devoid of worth.
Engrossed by mean and selfish ends.
Whose heart expands not, those he lov'd, to aid;
Never may I lament attachments thus repaid.
[tr. Wodhull (1782)]

Unpitied may he die,
Who to a friend assistance can deny;
Nor, to afflicted virtue kind,
Unlocks the treasures of his mind!
[tr. Potter (1814)]

Let shameful blight
Slay him who gives not friends their right,
Unlocking them his heart's pure store:
Let him be friend of mine no more.
[tr. Webster (1868)]

May he perish and find no favour, whoso hath not in him honour for his friends, freely unlocking his heart to them. Never shall he be friend of mine.
[tr. Coleridge (1891)]

Thankless may he perish who desires not to assist his friends, having unlocked the pure treasures of his mind; never shall he be friend to me.
[tr. Buckley (1892)]

But he, who regardeth not friends, accursed may he perish, and hated,
Who opes not his heart with sincerity's key to the hapless-fated --
Never such shall be friend of mine!
[tr. Way (Loeb) (1894)]

Ah, but the man -- cursèd be he,
Cursèd beyond recover,
Who openeth, shattering, seal by seal,
A friend's clean heart, then turns his heel,
Deaf unto love: never in me
Friend shall he know nor lover.
[tr. Murray (1906)]

Perish the fiend! whose iron heart
To fair Affection’s truth unknown,
Bids her he fondly lov’d depart,
Unpitied, helpless, and alone;
Who ne’er unlocks with silver key,
The milder treasures of his soul;
May such a friend be far from me,
And Ocean’s storms between us roll!
[tr. Byron (1907)]

O let him die ungraced whose heart
Will not reward his friends,
Who cannot open an honest mind
No friend will he be of mine.
[tr. Warner (1944)]

May dishonor and ruin fall on the man
Who, having unlocked the secrets
Of a friend's frank heart, can then disown him!
He shall be no friend of mine.
[tr. Vellacott (1963)]

Perish unloved the one
who does not unlock a pure heart to friends;
No friend of mind will he ever be.
[tr. Podlecki (1989)]

May that man die unloved who cannot honor his friends, unlocking to them his honest mind. To me at any rate he shall never be friend.
[tr. Kovacs (Loeb) (1994)]

Untouched by grace or favour may he die, the man who cannot honour his loved ones, by opening a heart that harbours no guile! Never shall he be friend of mine.
[tr. Davie (1996)]

Without grace may he perish who
does not treat his loved ones honorably
unbolting his heart in pure love.
He will never be a friend of mine.
[tr. Luschnig (2007)]

The man who shames his family,
who does not open up his heart
and treat them in all honesty --
may he perish unlamented.
With him I never could be friends.
[tr. Johnston (2008)]

May an ungrateful person be destroyed, one who does not honour family and friends when he has opened up their hearts and found them pure; may such a person never be my friend.
[tr. Ewans (2022)]

May he perish without grace [kharis], whoever could treat his philoi without timē, not opening the key of his phrenes. Never will he be philos to me.
[tr. Coleridge / Ceragioli / Nagy / Hour25]

May that man die unloved who cannot honour his friends, unlocking to them his honest mind. To me at any rate he shall never be a friend.
[tr. Kovacs / Zhang / Rogak]