What may not be done during Prayer and what is permitted - Section 3 — Mishkat al-Masabih 1011

Jabir said, “I used to pray the noon prayer with God’s Messenger, and would take a handful of pebbles to cool them in my palm and lay them down to put my forehead on them when prostrating myself because of the excessive heat.” Abu Dawud transmitted it, and Nasa’i transmitted something similar.