What Gautam Buddha said about "self", in Chapter Three of the Mahayana Mahaparinirvana Sutra?
The Buddha would have spoken about self as reference point. This is using conventional language and terms to explain something. Without using conventional language as medium you cannot communicate and when using conventional languages you end up using conventional terms. It is very had to have a vocabulary in terms of ultimate realities since  only few have experienced it any terms coined will not have bearing on people who has not experienced it. Since the Dhamma is taught for people who has not experienced the ultimate realities it should be in conventional terms.

Having said that any conception that there is a self or there is not self is an extreme view and also conceptual construction.


  The second mistaken inference is that, given the thoroughness with which the Buddha teaches not-self, one should draw the inference that there is no self. This inference is treated less explicitly in this discourse, although it is touched upon briefly in terms of what the Buddha teaches here and how he teaches.


Alagaddupama Sutta - Translator's Introduction by Thanissaro Bhikkhu

Also see: Sutta references which Discuss Self and Not Self under Different Contexts