Sunan An-Nasai, Chapter: The Book of the Times (of Prayer)

"Al-Hajjaj arrived, and we asked Jabir bin Abdullah, who said: 'The Messenger of Allah (saw) prayed Zuhr at the time of intense heat,* and Asr when the sun was white and clear, and Maghrib when the sun set, and with Isha it would depend - if he saw that the people had gathered, he would pray early, and if he saw that they had not come yet, he would delay it.'" (Sahih) *Meaning, at the earliest time.