Symbolism, Imagery, Allegory
There’s a bunch of worry over where Oedipus is going to be buried, and he’s not even dead yet. First Creon wants him to come back to Thebes so that he can be buried “near the land of Cadmus, so that they / Might have sway over you! But you would not cross the borders of the land” (399-400). This is because Oedipus is cursed, on account of having killed his father and married his mother. The Gods don't just forget when something like that goes down—it's all kinds of wrong.
The Thebans believe that if they let him back into their land, he’ll curse them, which explains why people don't want him crossing the borders of the land. But they do want to have sway over his grave because, as Ismene explains, “Should your tomb suffer misfortune, it will bring a heavy burden for them” (402). Graves are super sacred for the ancient Greeks, so even if a guy is cursed, you can’t have people tampering with his final resting spot and expect to get away with it.
Oedipus has his own ideas about where he should be buried though. He promises Theseus that if he protects him, he’ll offer his “miserable body” as “a gift to you” (576-77). Not exactly a conventional hostess gift, but Theseus is interested. It turns out that Oedipus’ body will be a source of superpowers to whoever is ruling Athens.
When Oedipus is on the verge of dying, he finally explains his weird offering to Theseus:
I myself will immediately lead the way,
Untouched by a guide, to the place where I must die.
Never tell this to anyone among humans—
Neither where it has been hidden nor in what region it lies,
So that this may always provide you with a strength
That surpasses many shields and the foreign spears of many neighbors. (1520-25)
We don’t think Creon knows about these super powers; he genuinely is motivated by fear when he tries to control Oedipus’ final resting place. But Theseus does keep the secret and does pretty well for himself, all thanks to showing mercy to a wandering soul.