Clearly every text is going to be different in terms of line numbers and location of specific parts of the drama, so it might be more use to you if I locate this speech in relation to where it comes in the actino of the play. Oedipus utters these lines after the Chorus gives us its first interlude in the play, and these lines are actually part of a much longer speech that Oedipus makes having been told by Creon that the plague that has befallen Thebes is actually the result of the unpunished murder of the original king of Thebes, Laius. Oedipus says the following lines:
And on the murderer this curse I lay
(On him and all the partners in his guilt):—
Wretch, may he pine in utter wretchedness!
And for myself, if with my privity
He gain admittance to my hearth, I pray
The curse I laid on others fall on me.
There is of course massive irony in this speech, as Oedipus not only delievers a curse on himself but also wishes that curse to fall on him if the murderer is given hospitality in his home. This play has been described as a detective mystery where the detective is made to realise that he is the criminal he is looking for. Such lines therefore have tremendous dramatic irony.
Oedipus promises to place a curse and punishment on the murderer (as he doesn't realize he is the murderer).
"Now my curse on the murderer. Whoever he is..." this can be found in line 280.