AGAMEMNON: Perhaps, for you, barbarians, it is easy to kill your guests but for us, Greeks, this is a thing of shame. How, then can I escape blame if I do not judge you guilty? I can’t do it. Since you could endure performing such a dishonourable deed, then you must also endure its awful consequences.

[ἈΓΑΜΈΜΝΩΝ: τάχ᾽ οὖν παρ᾽ ὑμῖν ῥᾴδιον ξενοκτονεῖν:
ἡμῖν δέ γ᾽ αἰσχρὸν τοῖσιν Ἕλλησιν τόδε.
πῶς οὖν σε κρίνας μὴ ἀδικεῖν φύγω ψόγον;
οὐκ ἂν δυναίμην. ἀλλ᾽ ἐπεὶ τὰ μὴ καλὰ
πράσσειν ἐτόλμας, τλῆθι καὶ τὰ μὴ φίλα.]

Euripides (485?-406? BC) Greek tragic dramatist

Hecuba [Hekabe; Ἑκάβη], l. 1247ff (c. 424 BC) [tr. Theodoridis (2007)]
    (Source)

Passing judgment on Polymestor for the death of Hecuba's son and theft of the Trojan treasure entrusted to him.

(Source (Greek)). Alternate translations:

Perhaps the murder of your guests seems light,
We Greeks esteem it base. If I acquit thee
How shall I scape reproach? Indeed, I cannot:
since thou hast dar'd to perpetrate the crime,
Endure the consequences.
[tr. Wodhull (1809)]

Perhaps with you it is a slight thing to kill your guests; but with us Grecians this thing is abhorred. How then, in giving my decision that thou hast not injured, can I escape blame? I can not; but as thou hast dared to do things dishonorable, endure now things unpleasant.
[tr. Edwards (1826)]

Haply with you guest-murder is as nought,
But to us which be Greeks foul shame is this.
How can I uncondemned adjudge thee guiltless?
I cannot. Forasmuch as thou hast dared
To do foul deeds, even drain thy bitter cup.
[tr. Way (Loeb) (1894)]

Perhaps among you it is a light thing to murder guests, but with us in Hellas it is a disgrace. How can I escape reproach if I judge you not guilty? I could not. No, since you endured your horrid crime, endure as well its painful consequence.
[tr. Coleridge (1938)]

Perhaps you think it is a trifling matter
to kill a guest.
We Greeks call it murder.
How, therefore, could I acquit you now
without losing face among men?
I could not do it.
You committed a brutal crime; therefore accept
the consequences of your act.
[tr. Arrowsmith (1958)]

Perhaps for lesser breeds it's no great thing to kill a guest, but to us Greeks it is. If I say you did no wrong I can't escape the censure and the blame that I'll incur. Since you were tough enough to do such deeds be tough enough to suffer the results.
[tr. Harrison (2005)]

Maybe you think
killing a guest -- in this case a child who’d been
put in your care -- is a small matter in the larger
scheme of things. But we Greeks think of it
as heinous murder. How could I rule you innocent
and maintain a shred of credibility? I can’t.
You committed a brutal crime; be prepared,
therefore, for a justly brutal punishment.
[tr. Karden/Street (2011)]