Allāhumma inna fī dhimmatik, wa ḥabli jiwārik, faqihi min fitnati ‘l-qabri wa `adhābin-nār, wa anta ahlu ‘l-wafā'i wa ‘l-ḥaqq. Faghfir lahu warḥamh innaka anta ‘l-Ghafūrur-Raḥīm. O Allah, surely is under Your protection, and in the rope of Your security, so save him from the trial of the grave and from the punishment of the Fire. You fulfill promises and grant rights, so forgive him and have mercy on him. Surely You are Most Forgiving, Most Merciful. Reference: Ibn Majah, Abu Dawud 3/211. See also Al Albani, Sahih Ibn Majah 1/251.
Source: sunnah.com
Other translations
Arabic
اللهُـمِّ إِنَّ فُلانَ بْنَ فُلانٍ في ذِمَّـتِك ، وَحَبْـلِ جِـوارِك ، فَقِـهِ مِنْ فِتْـنَةِ الْقَـبْرِ وَعَذابِ النّـار ، وَأَنْتَ أَهْلُ الْوَفـاءِ وَالْـحَقِّ ، فَاغْفِـرْ لَهُ وَارْحَمْـهُ ، إِنَّكَ أَنْتَ الغَـفورُ الـرَّحيم
sunnah.com