It's on page 72 in the book, assuming there's only one edition. It seems like Santopietro is saying that it's from the original novel, but it's not in there.
Thanks for bringing this up. Some additional searching has turned up a book of movie quotes that has the same quote, this time sourced to GF3. Looks like one of them messed up, and the other copied from the first. Thanks!
I just found the book, and checked for you, you are right, it is on page 72, it is attributed to Puzo's book, not The Godfather movie.
