From a reader:
At my parish’s Extraordinary Form Mass this morning, the priest, I think accidentally, used the readings and prayers for the Sixth Sunday after Pentecost instead of those for the Fifth Sunday. Did this affect the validity of the Mass? I’m fairly certain it wouldn’t had it been in the Ordinary Form, but am not sure what the rubrics state for older form.
No, this would not affect the validity of Mass.
It did not affect your Mass obligation either.
Of course, if the priest is constantly doing this, then perhaps someone should double-check which Ordo he is using!
These things happen occasionally.
I would not give this a second thought.