Ibn ‘Abbās said that one of the Prophet's companions set up his tent over a grave without realising that it was a grave, and it contained a man who was reciting the sūra, “Blessed is He in whose hand is the kingdom,” up to the end. He went and told the Prophet, who said, “It is the defender; it is the protector which is protecting him from God's punishment.” Tirmidhi transmitted it, .saying this is a gharīb tradition.
Source: sunnah.com
Other translations
Arabic
وَعَنِ ابْنِ عَبَّاسٍ قَالَ: ضَرَبَ بَعْضِ أَصْحَابِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ خِبَاءَهُ عَلَى قَبْرٍ وَهُوَ لَا يَحْسَبُ أَنَّهُ قَبْرٌ فَإِذَا فِيهِ إِنْسَان يَقْرَأُ سُورَةَ (تَبَارَكَ الَّذِي بِيَدِهِ الْمُلْكُ) حَتَّى خَتَمَهَا فَأَتَى النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَأَخْبَرَهُ فَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «هِيَ الْمَانِعَةُ هِيَ الْمُنْجِيَةُ تُنْجِيهِ مِنْ عَذَابِ الْقَبْر» . رَوَاهُ التِّرْمِذِيّ وَقَالَ: هَذَا حَدِيث غَرِيب
sunnah.com