ENOfficial
It was narrated that: Al-Bara said about Allah will keep firm those who believe, with the word that stands firm in this world and in the Hereafter "It was revealed concerning the torment of the grave.
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا إِسْحَاقُ بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ، عَنْ سُفْيَانَ، عَنْ أَبِيهِ، عَنْ خَيْثَمَةَ، عَنِ الْبَرَاءِ، قَالَ { يُثَبِّتُ اللَّهُ الَّذِينَ آمَنُوا بِالْقَوْلِ الثَّابِتِ فِي الْحَيَاةِ الدُّنْيَا وَفِي الآخِرَةِ } قَالَ نَزَلَتْ فِي عَذَابِ الْقَبْرِ .
sunnah.com