Muwatta Malik #28

Malik related to us from Abdullah ibn Yazid the mawla of al-Aswad ibn Sufyan, from Abu Salama ibn Abd ar-Rahman from Muhammad ibn Abd ar-Rahman ibn Thawban from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, "When the heat is fierce delay the prayer until it gets cooler, for scorching heat is a part of the blast of Jahannam." He added, "The Fire complained to its Lord, so He allowed it two breaths in each year, a breath in winter and a breath in summer."