Hadithcore
Musnad Ahmad 1411
sahih

It was narrated that az-Zubair bin al-"Awwam (رضي الله عنه) said:

We used to pray Jumu’ah with the Prophet (ﷺ), then we would leave and seek the shade of the fortress, but we would not find any shade except (an area) the width of our feet.

References1 variant
Arabic/English book
Book 7, Hadith 1411