اَللّٰهُمَّ إِنَّ فُلَانَ بْنَ فُلَانٍ فِيْ ذِمَّتِكَ، وَحَبْلِ جِوَارِكَ، فَقِهِ مِنْ فِتْنَةِ الْقَبْرِ، وَعَذَابِ النَّارِ، وَأَنْتَ أَهْلُ الْوَفَاءِ وَالْحَقِّ، فَاغْفِرْ لَهُ وَارْحَمْهُ إِنَّكَ أَنْتَ الْغَفُوْرُ الرَّحِيْمُ
O Allah, surely [name the person] 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.
Ibn Majah, Abu Dawud 3/211. See also Al Albani, Sahih Ibn Majah 1/251