A hadith like this has been reported on the authority of Nafi` with the same chain of transmitters (and the words are):
"I think Ibn `Umar said: The seventieth part from Prophecy."
Reference: Sahih Muslim 2265 c
In-book reference: Book 42, Hadith 22
USC-MSA web (English) reference(deprecated numbering scheme): Book 29, Hadith 5634