Where is the following Buddhist quote from and how do I reference it?

It's in the Anatta-lakkhana Sutta.

Here's the full text: https://www.accesstoinsight.org/tipitaka/sn/sn22/s...

It very well could be a fake quote.

Try googling it - type in Buddhist and some key words of the quote. It's amazing how you can often get things this way

This is a tricky question as I'm afraid many Vedic religions might have such a quote as this in both Sanskrit and Pali (Hindu and Buddhist) texts.

Check the Bhagavad Gita; the Srimad Bhagavatam; the Tibetan Book of the Dead and other such books. Many of these contain the central theme that self is an illusion and that identifications are false. Indeed, this concept is also found in Advaita (the via negativa - Latin for way of negation) where self is found not by identification but by divesting the mind of the false assumptions and identifications that form the image of the self.

The thing about references is that you need to cite the page and paragraph. If you cite a large book or one volume in a large book, you'll be asked to pinpoint the reference. Tricky if you have cheated.