The Messenger of Allah ﷺ came out to the people of Quba while they were performing the Duha prayer and said, "The prayer of those who turn often to Allah is when the young camels feel the heat of the sand."
حدثنا وكيع حدثنا هشام الدستوائي عن القاسم بن عوف الشيباني
خرج رسول الله ﷺ على أهل قباء وهم يصلون الضحى فقال صلاة الأوابين إذا رمضت الفصال من الضحى
Its isnad is sahih. It is found in Muslim 1/515, no. 748, in the chapter on travelers, "The prayer of those who turn to Allah in repentance, when the young camels' feet burn from the heat." Also in Ibn Khuzayma 2/229, no. 1227, and Bayhaqi 3/49.His statement, "The prayer of those who turn to Allah in repentance, when the young camels' feet burn from the heat," means, when the heat becomes intense, the young camels kneel down from the burning ground, and "fisal" refers to the young of camels.