Sahih Muslim
The Book Giving Description of the Day of Judgement, Paradise and Hell (Kitab Sifat Al-Qiyamah wal Janna wan-Nar)
Book Number: 039 / Hadith Number: 6709
'A'isha reported: I asked Allah's Messenger (may peace be upon him) about the words of Allah, the Exalted and Glorious:" The day when the earth would be changed for another earth and Heaven would be changed for another Heaven (XiV. 48), (and inquired: ) (Allah's Messenger), where would the people be on tnat day? He said: They would be on the Sirit.