Abu Musa Ashari reported,

The Prophet ﷺ called for water, performed ablution, then raised his hands and said, "Allah, forgive Ubayd Abu Amir." I saw the whiteness of his armpits as he said, "Allah, place him on the Day of Resurrection above many of Your creation among mankind."

Azami 10882

Sahih

عن أبي موسى الأشعري قال

دعا النبي ﷺ بماء فتوضأ، ثم رفع يديه فقال: اللهم اغفر لعبيد أبي عامر. ورأيت بياض إبطيه، فقال: اللهم اجعله يوم القيامة فوق كثير من خلقك من الناس.

الأعظمي 10882صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Supplications, remembrances, and prayer upon the chosen Prophet ﷺ
Chapter
Etiquette of supplication
Section
Recommendation of wudu when supplicating
Numbering
Jami al-Kamil 10882 (2nd edition)
Azami 10882