Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1291
Abu Huraira reported: The Messenger of Allah (may peace be upon him) said: When it is hot, make delay (in the noon prayer) till it cools down, for the intensity of beat is from the Exhalation of Hell; and lie also mentioned that the Hellfire complained to the Lord (about the congested atmosphere) and so it was permitted to take two exhalation during the whole year, one exhalation during the winter and one exhalation during the summer.