the Prophet used to seek refuge with Allah from the torment of the grave and the trial of the Dajjal, and he said: "You will be tested in your graves." (Using translation from Nasāʾī 2065)  

أَنَّ النَّبِيَّ ﷺ كَانَ يَسْتَعِيذُ بِاللهِ مِنْ عَذَابِ الْقَبْرِ وَمِنْ فِتْنَةِ الدَّجَّالِ وَقَالَ «إِنَّكُمْ تُفْتَنُونَ فِي قُبُورِكُمْ»