Waki' bin al-Jarrah وكيع بن الجراح · The Book of the Prayer

"A man came to the Prophet and asked him about the times of the prayer. He said: 'Pray with us for two days.' When the sun passed its zenith he commanded Bilal to call the Adhan, then he commanded him to give the Iqamah for Zuhr; then he commanded him to give the Iqamah for 'Asr when the sun was high and clearly white. Then he commanded him to give the Iqamah for Maghrib when the sun had set; then…

"The Messenger of Allah said: 'Wait for it to cool down before you pray the Zuhr.'"