Sahih al-Bukhari, Hadith 4440 ⓘ
Narrated `Aisha: I heard the Prophet and listened to him before his death while he was leaning his back on me and saying, "O Allah! Forgive me, and bestow Your Mercy on me, and let me meet the (highest) companions (of the Hereafter)." (See the Qur'an (4:69) and Hadith #4435)
حَدَّثَنَا مُعَلَّى بْنُ أَسَدٍ، حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ مُخْتَارٍ، حَدَّثَنَا هِشَامُ بْنُ عُرْوَةَ، عَنْ عَبَّادِ بْنِ عَبْدِ اللَّهِ بْنِ الزُّبَيْرِ، أَنَّ عَائِشَةَ، أَخْبَرَتْهُ أَنَّهَا، سَمِعَتِ النَّبِيَّ صلى الله عليه وسلم وَأَصْغَتْ إِلَيْهِ قَبْلَ أَنْ يَمُوتَ، وَهْوَ مُسْنِدٌ إِلَىَّ ظَهْرَهُ يَقُولُ " اللَّهُمَّ اغْفِرْ لِي وَارْحَمْنِي، وَأَلْحِقْنِي بِالرَّفِيقِ " .
also referenced under: Book 64, Hadith 461 (In-Book) & Volume 5, Book 59, Hadith 724 (USC-MSA)