It is narrated from Sayyiduna Abu Mas'ud (may Allah be pleased with him) that he said: I saw the Messenger of Allah (peace and blessings be upon him); he would pray Zuhr after the sun had declined, though occasionally he would delay it a little in severe heat, and he would pray Asr at a time when the sun was quite clear (that is, its heat was still present). A man, after finishing the prayer, would reach Dhu al-Hulayfah before sunset, while it is at a distance of six miles from Madinah. Then he mentioned the complete hadith.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2078