Sahih al-Bukhari 539
صحيح البخاري#539SahihNarrated Abu Dhar Al-Ghifar:We were with the Prophet (ﷺ) on a journey and the Mu'adh-dhin (call maker for the prayer) wanted to pronounce the Adhan (call) for the Zuhr prayer. The Prophet (ﷺ) said, 'Let it become cooler." He again (after a while) wanted to pronounce the Adhan but the Prophet (ﷺ) said to him, "Let it become cooler till we see the shadows of hillocks." The Prophet (ﷺ) added, "The severity of heat is from the raging of the Hell-fire, and in very hot weather pray (Zuhr) when it becomes cooler
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 9:16