Reference : Hisn al-Muslim 155

اللهُـمِّ اغْفِـرْ لِـفلان (باسـمه)
وَارْفَعْ دَرَجَتَـهُ في المَهْـدِييـن ، 
وَاخْـلُفْـهُ في عَقِـبِهِ في الغابِـرين، 
وَاغْفِـرْ لَنـا وَلَـهُ يا رَبَّ العـالَمـين،
وَافْسَـحْ لَهُ في قَبْـرِهِ وَنَـوِّرْ لَهُ فيه
Allāhumma’ghfir li (name of the person) 
warfa` darajatahu fi ‘l-mahdiyyīn,
wakhlufhu fī `aqibihi fi ‘l-ghābirīn, 
wagh’fir-lanā wa lahu yā Rabba ‘l-`ālamīn, 
wafsaḥ lahu fī qabrihi wa nawwir lahu fīh.


O Allah, forgive [name of the person]
and elevate his station among those who are guided. 
Send him along the path of those who came before, 
and forgive us and him, O Lord of the worlds.
Enlarge for him his grave, and shed light upon him in it.

Reference:
Muslim 2/634.

Chapter: When closing the eyes of the deceased