Question is in the title. I remember reading that statement in a Theravada Buddhist book or PDF file but now I can't seem to find it.
Help would be much appreciated.
It's in the Mahaparinibbana Sutta. In whichever teaching and discipline/ training the Noble Eightfold Path is not found, the four types of enlightened persons cannot be found also.
“Subhadda, in whatever teaching and training the noble eightfold path is not found, there is no true ascetic found, no second ascetic, no third ascetic, and no fourth ascetic. In whatever teaching and training the noble eightfold path is found, there is a true ascetic found, a second ascetic, a third ascetic, and a fourth ascetic. In this teaching and training the noble eightfold path is found. Only here is there a true ascetic, here a second ascetic, here a third ascetic, and here a fourth ascetic. Other sects are empty of ascetics.