Sunan an-Nasa'i, Volume 2, Book 12, Hadith 1082 (DarusSalam) ⓘ

It was narrated that Jabir bin 'Abdullah said: "We used to pray Zuhr with the Messenger of Allah and I would take a handful of pebbles in my hand to cool them down, then I would pass them from one hand to the other, and when I prostrated I would put them down to lay my forehead on them."

أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا عَبَّادٌ، عَنْ مُحَمَّدِ بْنِ عَمْرٍو، عَنْ سَعِيدِ بْنِ الْحَارِثِ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ، قَالَ كُنَّا نُصَلِّي مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم الظُّهْرَ فَآخُذُ قَبْضَةً مِنْ حَصًى فِي كَفِّي أُبَرِّدُهُ ثُمَّ أُحَوِّلُهُ فِي كَفِّي الآخَرِ فَإِذَا سَجَدْتُ وَضَعْتُهُ لِجَبْهَتِي ‏.‏