Supplications of the terminally ill patient

أَللّٰهُـمَّ اغْفِـرْلِيْ وَارْحَمْـنِيْ وَأَلْحِقْـنِيْ بِالرَّفِيْقِ الْأَعْلٰى

O Allah, forgive me and have mercy upon me and join me with the highest companions (in Paradise).

[Sahih Bukhari – 5674]

لَآ إِلٰهَ إِلَّا اللهُ، إِنَّ لِلْمَـوْتِ لَسَكَرَاتٍ

There is none worthy of worship but Allah, surely death has agonies.
As he was dying, the Prophet ﷺ dipped his hands in water and wiped his face saying above Dua.

[Sahih Bukhari – 4449]

لَآ إِلٰهَ إِلَّا اللهُ وَاللهُ أَكْبَـرُ، لَآ إِلٰهَ إِلَّا اللهُ وَحْـدَهٗ لَا شَرِيْكَ لَهٗ، لَآ إِلٰهَ إِلَّا اللهُ لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ، لَآ إِلٰهَ إِلَّا اللهُ وَلَا حَـوْلَ وَلَا قُـوَّةَ إِلَّا بِاللهِ

There is none worthy of worship but Allah, Allah is the Greatest. None has the right to be worshipped but Allah alone. None has the right to be worshipped but Allah alone, Who has no partner. There is none worthy of worship but Allah, His is the dominion and His is the praise. There is none worthy of worship but Allah, there is no power and no might except with Allah.

[Jame Tirmizi – 3430]