Sunan Ibn Majah, Chapter: The Book of the Sunnah

"I was in Batha with a group of people, among whom was the Messenger of Allah (saw). A cloud passed over him, and he looked at it and said: 'What do you call this?' They said: 'Sahab (a cloud).' He said: 'And Muzn (rain cloud).' They said: 'And Muzn.' He said: 'And Anan (clouds).' Abu Bakr said: 'They said: 'And 'Anan.'" He said: 'How much (distance) do you think there is between you and the heavens?' They said: 'We do not know.' He said: 'Between you and it is seventy-one, or seventy-two, or seventy-three years, and there is a similar distance between it and the heaven above it (and so on)' until he counted seven heavens. 'Then above the seventh heaven there is a sea, between whose top and bottom is a distance like that between one heaven and another. Then above that there are eight (angels in the form of) mountain goats. The distance between their hooves and their knees it like the distance between one heaven and the next. Then on their backs is the Throne, and the distance between the top and the bottom of the Throne is like the distance between one heaven and another. Then Allah is above that, the Blessed and Exalted." (Da'if)