Imām Bukhārī narrates: Ādam ibn Abī Iyās narrated to us, he said: Shu'bah narrated to us, he said: Al-Muhājir Abū al-Hasan narrated to us, who is the freed slave of Banū Taim Allāh, he said: I heard Zaid ibn Wahb, from Abū Dharr al-Ghifārī, may Allāh be pleased with him, he said:
We were with the Prophet ﷺ on a journey. So the mu'adhdhin intended to give the adhān for Zuhr, so the Prophet ﷺ said: In the cooler time. He again intended to give the adhān, so he said: In the cooler time, until we saw the shadow of the hills. Then the Prophet ﷺ said: The intensity of heat is from the raging of Jahannam, so when the heat is intense, pray the prayer in the cooler time.
Ibn 'Abbās said: "Tatafaya" means: they were inclining.
Reference: Sahih Al Bukhari 539