The final supplication of the Holy Prophet (sa)

عَنْ عَبَّادِ بْنِ عَبْدِ اللّٰهِ بْنِ الزُّبَيْرِ، أَنَّ عَائِشَةَ، أَخْبَرَتْهُ أَنَّهَا، سَمِعَتِ النَّبِيَّ صلّى اللّٰهُ عَلَيْهِ وَسَلَّمَ وَأَصْغَتْ إِلَيْهِ قَبْلَ أَنْ يَمُوتَ، وَهْوَ مُسْنِدٌ إِلَىَّ ظَهْرَهُ يَقُولُ: اللّٰهُمَّ اغْفِرْلِي وَارْحَمْنِي، وَأَلْحِقْنِي بِالرَّفِيقِ.‏

It is narrated by Abbad ibn Abd Allah ibn az-Zubayr that Hazrat Aisha^ra informed him that she heard the Holy Prophet^sa and listened to him carefully before his demise while he was leaning his back on her and saying, “O Allah! Forgive me, and bestow mercy on me, and join me with [Yourself], the [Highest] Companion.”

(Sahih al-Bukhari, Kitab al-maghazi, Bab maradi n-nabiyyi^sa wa wafatah)