Say "Allāhu Akbar", then make sincere duʿāʾ for the deceased. The Prophet ﷺ taught:
For a male deceased
اللَّهُمَّ اغْفِرْ لَهُ وَارْحَمْهُ، وَعَافِهِ وَاعْفُ عَنْهُ، وَأَكْرِمْ نُزُلَهُ، وَوَسِّعْ مُدْخَلَهُ،
وَاغْسِلْهُ بِالْمَاءِ وَالثَّلْجِ وَالْبَرَدِ، وَنَقِّهِ مِنَ الْخَطَايَا كَمَا نَقَّيْتَ الثَّوْبَ
الأَبْيَضَ مِنَ الدَّنَسِ، وَأَبْدِلْهُ دَارًا خَيْرًا مِنْ دَارِهِ، وَأَهْلًا خَيْرًا مِنْ أَهْلِهِ،
وَزَوْجًا خَيْرًا مِنْ زَوْجِهِ، وَأَدْخِلْهُ الْجَنَّةَ، وَأَعِذْهُ مِنْ عَذَابِ الْقَبْرِ وَمِنْ عَذَابِ
النَّارِ
"O Allah, forgive him and have mercy on him, pardon him and grant him ease. Honor his resting place and expand
his entrance. Wash him with water, snow, and hail, and cleanse him of sins as a white garment is cleansed of
dirt. Grant him a home better than his home, a family better than his family, and a spouse better than his
spouse. Admit him into Paradise and protect him from the punishment of the grave and the torment of the Fire."
For a female deceased
اللَّهُمَّ اغْفِرْ لَهَا وَارْحَمْهَا، وَعَافِهَا وَاعْفُ عَنْهَا، وَأَكْرِمْ نُزُلَهَا، وَوَسِّعْ
مُدْخَلَهَا، وَاغْسِلْهَا بِالْمَاءِ وَالثَّلْجِ وَالْبَرَدِ، وَنَقِّهَا مِنَ الْخَطَايَا كَمَا نَقَّيْتَ
الثَّوْبَ الأَبْيَضَ مِنَ الدَّنَسِ، وَأَبْدِلْهَا دَارًا خَيْرًا مِنْ دَارِهَا، وَأَهْلًا خَيْرًا مِنْ
أَهْلِهَا، وَزَوْجًا خَيْرًا مِنْ زَوْجِهَا، وَأَدْخِلْهَا الْجَنَّةَ، وَأَعِذْهَا مِنْ عَذَابِ الْقَبْرِ
وَمِنْ عَذَابِ النَّارِ
"O Allah, forgive her and have mercy on her, pardon her and grant her ease. Honor her resting place and expand
her entrance. Wash her with water, snow, and hail, and cleanse her of sins as a white garment is cleansed of
dirt. Grant her a home better than her home, a family better than her family, and a spouse better than her
spouse. Admit her into Paradise and protect her from the punishment of the grave and the torment of the Fire."
For a child
اَللّٰهُمَّ اجْعَلْهُ فَرَطًا وَّذُخْرًا لِّوَالِدَيْهِ، وَشَفِيْعًا وَّمُجَابًا، اَللّٰهُمَّ ثَقِّلْ بِهٖ
مَوَازِيْنَهُمَا، وَأَعْظِمْ بِهٖ أُجُوْرَهُمَا، وَأَلْحِقْهُ بِصالِحِ الْمُؤْمِنِيْنَ، وَاجْعَلْهُ فِي
كَفَالَةِ إِبْرَاهِيْمَ، وَقِهِ بِرَحْمَتِكَ عَذَابَ الْجَحِيْمِ، وَأَبْدِلْهُ دَارًا خَيْرًا مِّنْ دَارِهٖ
وَأَهْلًا خَيْرًا مِّنْ أَهْلِهٖ، اَللّٰهُمَّ اغْفِرْ لِأَسْلَافِنَا وَأَفْرَاطِنَا وَمَنْ سَبَقَنَا
بِالْإِيْمَانِ
"O Allah, make him a preceding reward and a treasure for his parents and an answered intercessor. O Allah,
make him weigh heavily in their scales and magnify their reward. Make him join the righteous of the
believers. Place him in the care of Ibrāhīm. Save him by Your mercy from the torment of Hell. Give him a
home better than his home and a family better than his family. O Allah, forgive those who have gone before
us, our children lost by death, and those who have preceded us in faith."
al-Mughnī, Ibn Qudāmah 2/369