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".
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَهَارُونُ بْنُ عَبْدِ اللَّهِ، وَعَبْدُ بْنُ حُمَيْدٍ، قَالَ عَبْدٌ أَخْبَرَنَا وَقَالَ الآخَرَانِ، حَدَّثَنَا جَعْفَرُ بْنُ عَوْنٍ، أَخْبَرَنَا أَبُو عُمَيْسٍ، عَنْ عَبْدِ الْمَجِيدِ بْنِ سُهَيْلٍ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، قَالَ قَالَ لِيَ ابْنُ عَبَّاسٍ تَعْلَمُ - وَقَالَ هَارُونُ تَدْرِي - آخِرَ سُورَةٍ نَزَلَتْ مِنَ الْقُرْآنِ نَزَلَتْ جَمِيعًا قُلْتُ نَعَمْ . { إِذَا جَاءَ نَصْرُ اللَّهِ وَالْفَتْحُ} قَالَ صَدَقْتَ . وَفِي رِوَايَةِ ابْنِ أَبِي شَيْبَةَ تَعْلَمُ أَىُّ سُورَةٍ . وَلَمْ يَقُلْ آخِرَ .
sunnah.com