One of the major theme of the play is pride and this theme has been depicted in the given line.
Explanation:
'Oedipus Rex' is the play written by Sophocles. The meaning of Oedipus is 'swollen feet' and Rex means 'King.'
The play is about Oedipus, the protagonist of the play and the ultimate fulfillment of prophesy about him that he would kill his father and marry his mother. Oedipus, in his pride killed his father.
One of the major themes of the play is pride, a pride that goes before the fall of man. The given line reflects the pride of Oedipus of finding the culprit who killed King Laius, not for anyone else but for his own sake. The line reflects that Oedipus thinks of no one else but himself and is full of pride. Oedipus will remove 'this polluting stain' for no one else but for his own sake.