Imam Maalik مالك بن أنس بن مالك بن أبي عامر · The Book of the Prayer

The Messenger of Allah said: "When it is very hot, then wait for it to cool down before you pray, for intense heat is from the flaring up of the Hell-fire."

"The Prophet prayed the 'Asr when the sun was shining into my room and there were no shadows yet."