Ubaidullah b. 'Abdullah b. 'Utba reported:
Ibn Abbas said to me: Do you know-and in the words of Harun (another narrator): Are you aware of-the last Sura which was revealed in the Qur'an as a whole? I said: Yes," When came the help from Allah and the victory" (cx.). Thereupon, he said: You have told the truth. And in the narration of Abu Shaiba (the words are): Do you know the Sura? And he did not mention the words" the last one".
Reference: Sahih Muslim 3024 a
In-book reference: Book 56, Hadith 24
USC-MSA web (English) reference(deprecated numbering scheme): Book 43, Hadith 7174