Oedipus: Do not say you reverence heaven,
then do nothing but ignore what heaven says.
Make no mistake,
the gods' eyes see the just
and the gods' eyes see the unjust too,
and from that blazing gaze,
never on this earth,
will the wicked man escape by flight (280).
Oedipus: I saved
The city--I wish I had not--
And the prize for this has broken my heart (289).
Theseus: For I know too well that I am only a man.
The portion of your days today
cold be no less than mine tomorrow (290).
Oedipus: For tell me this:
Suppose my father by some oracle was doomed to die
by his own son's hand,
could you justly put the blame on me--
a babe unborn,
not yet begotten by a father,
not yet engendered in a mother's womb?
And if when born--as born I was to tragedy--
I met my father in a fight and killed him,
ignorant of what I did, to whom I did it,
can you still condemn an unwilled act? (305).
Oedipus at Colonus is the middle play of Sophocles' Theban Cycle, preceded by Oedipus Rex and followed by Antigone. In this play the exiled Oedipus is nearing death and he finally gets some revenge on the city (Thebes) and people (Creon, Eteocles, and Polyneices) who had wronged him and cast him into exile. By the time Sophocles wrote this play he was extremely elderly (he was in his 90s, and the play was actually first performed posthumously), and he seems to have a tremendous amount of sympathy for the elderly Oedipus, a man whose sufferings and dignity lend him an air almost of divinity. Indeed, the play talks of him becoming a talisman for whoever can win him to their side, and there is something of the saint's tale feel to Oedipus at Colonus. Early in the play, the titular character is somewhat pathetic--perhaps justifiably so, considering all he has suffered--and makes Theseus promise numerous times to protect him from the Thebans who want to capture him, so much so that Theseus at one point gets annoyed and tells Oedipus that the promise has already been made and not to ask again. However, as the play goes on and first Creon and then Polyneices come to try and bring Oedipus back, his power/authority/divinity grows, not just for the characters but for the audience/reader as well. This movement from pitiful exile to religious totem is one of Sophocles' most skillful sequences in any of his plays.
The movement and tone of this play is very different from its precursor or successor, both of which were written much earlier in Sophocles' life--Antigone was written while he was young, and Oedipus Rex at Sophocles' maturity as a playwright. Although the stories follow one another and are often referred to as a 'trilogy' or a 'cycle,' in reality they aren't. Unlike Aeschylus' Oresteia, which was written to be performed one following the other, each of the Theban plays was written to be performed with two other plays (and a satyr play) now all unknown. This gives us a really good insight into Greek drama, because we might as easily stick other plays under the umbrella of 'the Theban Cycle,' like Aeschylus' Seven Against Thebes, which fits into the plot between Sophocles' Oedipus at Colonus and Antigone. Other than a common authorship, there isn't much reason to think of Sophocles' Theban plays as a coherent unit--their styles are different, they were written throughout the course of an exceptionally long dramatic career, and the content doesn't exactly match up. It's highly unlikely that the Greeks thought of the plays as specifically connected in the way we tend to think of them today, because Greek authors used and reused material from myth, legend, history, and stories to construct plays that presented very similar content in (sometimes subtly, sometimes starkly) different ways. Likely Sophocles, who wrote over 120 plays, wrote more plays about the house of Oedipus, but these three are the only ones that survive.