When the heat is violent, offer (the Zuhr) prayer when it becomes fairly cool, for the violent heat comes from the bubbling over the Hell.
Sunan Abi Dawud Book 2, Hadith 12
← Previous Hadith We were in the company of the Prophet (ﷺ). The mu'adhdhin intended to call for the Zuhr prayer. He said: Make it cooler. He then intended to call for prayer. He said twice or thrice: Make it cooler. We then witnessed the shadow of the mounds. He then said: The intensity of heat comes from the bubbling over of the Hell ; so when the heat is violent, offer (the Zuhr) prayer when it becomes cooler.

Sunan Abi Dawud Book 2, Hadith 11 Next Hadith → Jabir b. Samurah reported that Bilal used to call for the noon prayer when the sun had declined.

Sunan Abi Dawud Book 2, Hadith 13