Musnad Ahmad 30:2825

I read to Abd al-Rahman: Malik, from Abdullah ibn Yazid, the freed slave of al-Aswad ibn Sufyan, from Abu Salamah ibn Abd al-Rahman and Muhammad ibn Abd al-Rahman ibn Thawban, from Abu Hurairah, who said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "When the heat is intense, then delay the prayer until it cools down, for the intensity of heat is from the scorching breath of Hell." And he mentioned: "That the Fire complained to its Lord, so He permitted it two breaths every year: one breath in the winter and one breath in the summer."