Sahih al-Bukhari 4364
Sahih al-Bukhari · Book 64: Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi) · The Hajj in which Abu Bakr led the people
Narrated Al-Bara:
حَدَّثَنِي عَبْدُ اللَّهِ بْنُ رَجَاءٍ ، حَدَّثَنَا إِسْرَائِيلُ ، عَنْ أَبِي إِسْحَاقَ ، عَنِ الْبَرَاءِ ـ رضى الله عنه ـ قَالَ آخِرُ سُورَةٍ نَزَلَتْ كَامِلَةً بَرَاءَةٌ، وَآخِرُ سُورَةٍ نَزَلَتْ خَاتِمَةُ سُورَةِ النِّسَاءِ {يَسْتَفْتُونَكَ قُلِ اللَّهُ يُفْتِيكُمْ فِي الْكَلاَلَةِ}
The last Sura which was revealed in full was Baraa (i.e. Sura-at-Tauba), and the last Sura (i.e. part of a Sura) which was revealed was the last Verses of Sura-an-Nisa':-- "They ask you for a legal decision. Say: Allah directs (thus) About those who have No descendants or ascendants As heirs." (4.177)