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).
Sahih al-Bukhari Book 59, Hadith 68