We were with the Messenger of Allah ﷺ on a journey, and one of us would place his hand on his head from the intense heat. None of us was fasting except the Messenger of Allah ﷺ and Abdullah bin Rawaha.
حدثنا أبو المغيرة حدثنا سعيد بن عبد العزيز حدثني إسماعيل بن عبيد الله عن أم الدرداء
كنا مع رسول الله ﷺ في سفر وإن أحدنا ليضع يده على رأسه من شدة الحر وما منا صائم إلا رسول الله ﷺ وعبد الله بن رواحة
Its isnad is sahih. Ismail bin Ubaydullah is the Damascene, Abu Abdul-Hameed. The hadith was narrated by Bukhari, 4/182, no. 1945, Fath, and Muslim, 2/790, no. 1122, and Abu Dawud, 2/329, and Ibn Majah, 1/532, no. 1663.