Sahih Bukhari
Beginning of Creation
Volume: 004 / Book Number: 054 / Hadith Number: 466
Narrated 'Abdullah bin Qais Al-Ashari:
The Prophet said, "A tent (in Paradise) is like a hollow pearl which is thirty miles in height and on every corner of the tent the believer will have a family that cannot be seen by the others." (Narrated Abu Imran in another narration, "(The tent is) sixty miles (in height)")