AIDS is just retribution for improper sexual conduct
"AIDS is just retribution for improper sexual conduct" is a quote popularly attributed to Mother Teresa. The popularity of the quote is due to its absurdity: it is generally used as evidence against Mother Teresa and the Catholic Church in general.
Issuepedia is currently investigating the accuracy of this quote.
Christopher Hitchens says of Teresa his in book The Missionary Position:
She also touched on AIDS, saying she did not want to label it a scourge of God but that it did seem like a just retribution for improper sexual conduct.
This is not a definitive quote (and I do not have the book to see what the context was). However, Michael Parenti says that she said something very similar in her 1979 Nobel Prize acceptance speech, video of which is available here. I have not yet watched this to see if this is accurate and what the full quote might be.
This skeptic site mentions the 1979 speech but does not cite it as the source for this quote. It does say, however:
When the International Health Organization honored Teresa in 1989, she spoke at length against abortion and contraception and called AIDS a "just retribution for improper sexual conduct".
I do not know if a recording or transcription of the 1989 speech is available, but it seems likely that there would be one somewhere.