Short answer
The best known dua is the one the Prophet ﷺ made in the janazah prayer: Allahumma ighfir lahu warhamhu wa 'afihi wa'fu 'anhu (O Allah, forgive him, have mercy on him, keep him safe and pardon him). You can make this dua, and any sincere dua for forgiveness, in any language and at any time.
Making dua for a dead Muslim is mustahabb (recommended) and its benefit reaches them. There is no fixed time, place or number, and dua in your own language is valid outside the prayer.
The four schools agree on this.
Explanation
Dua is the most precious gift you can give someone who has died. Their deeds have stopped, but your dua still reaches them. The four schools agree on this.
Dua from the janazah prayer. Allahumma ighfir lahu warhamhu, wa 'afihi wa'fu 'anhu, wa akrim nuzulahu, wa wassi' mudkhalahu. "O Allah, forgive him and have mercy on him, keep him safe and pardon him, honour his arrival and make his entrance wide." For a woman say laha and 'anha in place of lahu and 'anhu.
Dua when the eyes are closed. When Abu Salamah died, the Prophet ﷺ closed his eyes and prayed: "O Allah, forgive Abu Salamah, raise his rank among the rightly guided." You can say the same with your loved one's name.
Dua at the grave after burial. Stand for a while after the burial and ask Allah to keep them firm, because they are being questioned at that time. A simple dua is Allahumma thabbit-hu (O Allah, make him firm).
- For parents, see dua for deceased parents.
- For the full janazah duas in order, see how to pray janazah.
- For words to say to the family, see what to say when someone dies.
Keep making dua for them in your sujud, after your prayers, and on the nights when dua is answered. A righteous child who prays for a parent is one of the three things that keep benefiting a person after death.
The evidence
Quran, Surah Al-Hashr 59:10
وَٱلَّذِينَ جَآءُو مِنۢ بَعْدِهِمْ يَقُولُونَ رَبَّنَا ٱغْفِرْ لَنَا وَلِإِخْوَٰنِنَا ٱلَّذِينَ سَبَقُونَا بِٱلْإِيمَٰنِ وَلَا تَجْعَلْ فِى قُلُوبِنَا غِلًّۭا لِّلَّذِينَ ءَامَنُوا۟ رَبَّنَآ إِنَّكَ رَءُوفٌۭ رَّحِيمٌ ﴿١٠﴾
And [there is a share for] those who came after them, saying, "Our Lord, forgive us and our brothers who preceded us in faith and put not in our hearts [any] resentment toward those who have believed. Our Lord, indeed You are Kind and Merciful."
Believers pray for those who died before them.
Quran, Surah Ibrahim 14:41
رَبَّنَا ٱغْفِرْ لِى وَلِوَٰلِدَىَّ وَلِلْمُؤْمِنِينَ يَوْمَ يَقُومُ ٱلْحِسَابُ ﴿٤١﴾
Our Lord, forgive me and my parents and the believers the Day the account is established."
Ibrahim's dua includes parents and all believers.
Sahih Muslim 963
Sahih... اللهم اغفر له وارحمه وعافه واعف عنه ...
"O Allah, forgive him, have mercy on him, keep him safe and pardon him."
This is the Prophet's ﷺ own dua in a janazah prayer.
Sahih Muslim 920
Sahih... اللهم اغفر لأبي سلمة وارفع درجته في المهديين ...
"O Allah, forgive Abu Salamah and raise his rank among the rightly guided."
This dua was made right after death, naming the person.
Sunan Abi Dawud 3221
Graded sahih... استغفروا لأخيكم وسلوا له التثبيت فإنه الآن يسأل ...
"Ask forgiveness for your brother and ask that he be made firm, for he is being questioned now."
Dua at the grave after burial is sunnah.
Sahih Muslim 1631
Sahih... إذا مات الإنسان انقطع عنه عمله إلا من ثلاثة ...
"When a person dies, his deeds end except for three."
One of the three is a righteous child who prays for him.
Where the ruling is recorded
- al-Hidaya, Kitab al-Salah, Bab al-Jana'iz. The duas of the janazah prayer.
- Nur al-Idah with Maraqi al-Falah, Bab Ahkam al-Jana'iz. Dua for the dead after burial.
This answer is pending review by the scholars on our team. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.