From Sahih Bukhari (Hadith 3258):
Narrated Abu Dhar:While the Prophet (ﷺ) was on a journey, he said (regarding the performance of the Zuhr prayer), "Wait till it (i.e. the weather) gets cooler." He said the same again till the shade of the hillocks extended. Then he said, "Delay the (Zuhr) Prayer till it gets cooler, for the severity of heat is from the increase in heat of Hell (fire)
Reference: Bukhari 3258