Sahih Bukhari Volume 4, Book 54, Hadith Number 478.
Narated By Abu Said Al-Khudri : The Prophet said, “The people of Paradise will look at the dwellers of the lofty mansions (i.e. a superior place in Paradise) in the same way as one looks at a brilliant star far away in the East or in the West on the horizon; all that is because of their superiority over one another (in rewards).” On that the people said, “O Allah’s Apostle! Are these lofty mansions for the prophets which nobody else can reach? The Prophet replied,” No! “By Allah in whose Hands my life is, these are for the men who believed in Allah and also believed in the Apostles.”