Sahih al-Bukhari, Volume 8, Book 75, Hadith 392 (USC-MSA) ⓘ

Narrated Abu Musa: The Prophet asked for some water and performed the ablution, and then raised his hands (towards the sky) and said, "O Allah! Forgive `Ubaid Abi 'Amir." I saw the whiteness of his armpits (while he was raising his hands) and he added, "O Allah! Upgrade him over many of Your human creatures on the Day of Resurrection."

حَدَّثَنَا مُحَمَّدُ بْنُ الْعَلاَءِ، حَدَّثَنَا أَبُو أُسَامَةَ، عَنْ بُرَيْدِ بْنِ عَبْدِ اللَّهِ، عَنْ أَبِي بُرْدَةَ، عَنْ أَبِي مُوسَى، قَالَ دَعَا النَّبِيُّ صلى الله عليه وسلم بِمَاءٍ فَتَوَضَّأَ، ثُمَّ رَفَعَ يَدَيْهِ فَقَالَ ‏"‏ اللَّهُمَّ اغْفِرْ لِعُبَيْدٍ أَبِي عَامِرٍ ‏"‏‏.‏ وَرَأَيْتُ بَيَاضَ إِبْطَيْهِ فَقَالَ ‏"‏ اللَّهُمَّ اجْعَلْهُ يَوْمَ الْقِيَامَةِ فَوْقَ كَثِيرٍ مِنْ خَلْقِكَ مِنَ النَّاسِ ‏"‏‏.‏