The Prophet ﷺ said: When you pray over the dead, make a sincere supplication for him.  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ إِذَا صَلَّيْتُمْ عَلَى الْمَيِّتِ فَأَخْلِصُوا لَهُ الدُّعَاءَ  

I was present with Marwan who asked AbuHurayrah: Did you hear how the Messenger of Allah ﷺ used to pray over the dead? He said: Even with the words that you said. (The narrator said: They exchanged hot words between them before that.) Abu Hurairah said: O Allah, Thou art its Lord. Thou didst create it, Thou didst guide it to Islam, Thou hast taken its spirit, and Thou knowest best its inner nature and outer aspect. We have come as intercessors, so forgive him. Abu Dawud said: Shu'bah made a mistake in mentioning the name of 'Ali b. Shammakh. He said in his version: 'Uthman b. Shammas. Abu Dawud said: I heard Ahmad b. Ibrahim al-Mawsili say that Ahmad b. Hanbal said: In every meeting which I attended with Hammad b. Zaid he forbade to narrate this traditions from 'Abd al-Warith and Ja'far b. Sulaiman.  

شَهِدْتُ مَرْوَانَ سَأَلَ أَبَا هُرَيْرَةَ كَيْفَ سَمِعْتَ رَسُولَ اللَّهِ ﷺ يُصَلِّي عَلَى الْجَنَازَةِ قَالَ أَمَعَ الَّذِي قُلْتَ قَالَ نَعَمْ قَالَ كَلاَمٌ كَانَ بَيْنَهُمَا قَبْلَ ذَلِكَ قَالَ أَبُو هُرَيْرَةَ اللَّهُمَّ أَنْتَ رَبُّهَا وَأَنْتَ خَلَقْتَهَا وَأَنْتَ هَدَيْتَهَا لِلإِسْلاَمِ وَأَنْتَ قَبَضْتَ رُوحَهَا وَأَنْتَ أَعْلَمُ بِسِرِّهَا وَعَلاَنِيَتِهَا جِئْنَاكَ شُفَعَاءَ فَاغْفِرْ لَهُ  

When the Messenger of Allah ﷺ prayed over a dead person, he said: O Allah, forgive those of us who are living and those of us who are dead, those of us who are present and those of us who are absent, our young and our old, our male and our female. O Allah, to whomsoever of us Thou givest life grant him life as a believer, and whomsoever of us Thou takest in death take him in death as a follower of Islam. O Allah, do not withhold from us the reward (of faith) and do not lead us astray after his death.  

صَلَّى رَسُولُ اللَّهِ ﷺ عَلَى جَنَازَةٍ فَقَالَ اللَّهُمَّ اغْفِرْ لِحَيِّنَا وَمَيِّتِنَا وَصَغِيرِنَا وَكَبِيرِنَا وَذَكَرِنَا وَأُنْثَانَا وَشَاهِدِنَا وَغَائِبِنَا اللَّهُمَّ مَنْ أَحْيَيْتَهُ مِنَّا فَأَحْيِهِ عَلَى الإِيمَانِ وَمَنْ تَوَفَّيْتَهُ مِنَّا فَتَوَفَّهُ عَلَى الإِسْلاَمِ اللَّهُمَّ لاَ تَحْرِمْنَا أَجْرَهُ وَلاَ تُضِلَّنَا بَعْدَهُ  

The Messenger of Allah ﷺ led us in a ˹funeral˺ prayer of a Muslim and I heard him say, allāhuma inna [name of person] fī dhimmatik, faqihī fitnat al-qabr (O Allah, so and so, son of so and so, is under Your custodianship, so protect him from the trial in the grave.)” ʿAbd al-Raḥmān ˹in his version˺ said, “fī dhimmatik, wa-ḥabli jiwārik, faqihī min fitnat al-qabr, wa-ʿadhāb al-nār, wa-ʾanta ahl al-wafāʾ, wa-al-ḥamd; allāhuma fa-ighfir lahu wa-irḥamhu, innaka anta al-ghafūr al-raḥīm (under Your custodianship and ˹holding on to˺ the rope of Your security, so protect him from the trial in the grave and the torment of Hellfire. For You are most capable of fulfilling ˹duʿāʾ˺ and deserving of praise. O Allah, forgive him and show him mercy for You are the forgiving and the Most Merciful.)"  

صَلَّى بِنَا رَسُولُ اللَّهِ ﷺ عَلَى رَجُلٍ مِنَ الْمُسْلِمِينَ فَسَمِعْتُهُ يَقُولُ: «(اللَّهُمَّ إِنَّ /فُلاَنَ بْنَ فُلاَنٍ/ فِي ذِمَّتِكَ فَقِهِ فِتْنَةَ الْقَبْرِ.)» قَالَ عَبْدُ الرَّحْمَنِ: «(فِي ذِمَّتِكَ، وَحَبْلِ جِوَارِكَ، فَقِهِ مِنْ فِتْنَةِ الْقَبْرِ وَعَذَابِ النَّارِ، وَأَنْتَ أَهْلُ الْوَفَاءِ وَالْحَمْدِ، اللَّهُمَّ فَاغْفِرْ لَهُ وَارْحَمْهُ إِنَّكَ أَنْتَ الْغَفُورُ الرَّحِيمُ.)»