كتاب الْمَسَاجِدِ وَمَوَاضِعِ الصَّلاَةِ
5  
The Book of Mosques and Places of Prayer
(24)
Chapter: It is recommended to seek refuge with Allah from the punishment of the grave, the punishment of hell, the trials of life and death, the tribulation of the Dajjal and from sin and debt between the tashah-hud and the taslim
(24)
باب اسْتِحْبَابِ التَّعَوُّذِ مِنْ عَذَابِ الْقَبْرِ ‏
Sahih Muslim 586 b

Masruq reported this hadith on the authority of 'A'isha who said:

Never did he (the Holy Prophet) say prayer after this in which I did not hear him seeking refuge from the torment of the grave.
حَدَّثَنَا هَنَّادُ بْنُ السَّرِيِّ، حَدَّثَنَا أَبُو الأَحْوَصِ، عَنْ أَشْعَثَ، عَنْ أَبِيهِ، عَنْ مَسْرُوقٍ، عَنْ عَائِشَةَ، بِهَذَا الْحَدِيثِ وَفِيهِ قَالَتْ وَمَا صَلَّى صَلاَةً بَعْدَ ذَلِكَ إِلاَّ سَمِعْتُهُ يَتَعَوَّذُ مِنْ عَذَابِ الْقَبْرِ ‏.‏
Reference : Sahih Muslim 586b
In-book reference : Book 5, Hadith 160
USC-MSA web (English) reference : Book 4, Hadith 1215
  (deprecated numbering scheme)