['Abdullah] Ibn 'Umar narrated that the Messenger of Allah (s.a.w) said:
"Three shall be on dunes of musk" - it seems to me that he said:- "on the Day of Resurrection. The first and the last of peoples shall envy them: A man who calls to the five [prayers] every day and night; a man who leads a group of people and they are pleased with him, and a slave who fulfills the right of Allah and the right of his masters." (IT)
English reference (IT): Vol. 4, Book 12, Hadith 2566 (IT)
Arabic reference (IT): Book 38, Hadith 2765 (IT)