This quotation comes from Aeschylus' Agamemnon, which was first staged in 458 BCE. These lines are spoken by Chorus (or the Chorus Leader in some translations), who are addressing Agamemnon at lines 807-809 in the Greek text. Agamemnon has just returned from Troy and the Chorus of elderly citizens from Argos have been giving him a rather lukewarm welcome home.
The words of the elders foreshadow the doom that awaits Agamemnon. He is about to learn that while he was at Troy, his wife Clytemnestra has been having an affair with Aegisthus and they are about to play him false in the most extreme way possible: they are going to kill him.
Indeed, Agamemnon is next met by his wife Clytemnestra, who lures him into the palace to his doom. After Agamemnon enters the palace, Clytemnestra utters an ominous prayer:
O Zeus, Zeus, who accomplishes all things,
answer my prayers. Take care to bring about
all things that reach fulfillment through your will.
(Ian Johnston translation)