Musnad Abu Ya'la al-Mawsili 148:76

Abu Khaythama narrated to us, Yahya narrated to us, from Shu'bah, from Hamzah al-'A'idhi, who said: I heard Anas bin Malik say: When the Messenger of Allah (peace and blessings of Allah be upon him) would stop at a place, he would not depart from it until he had prayed Dhuhr. He said: A man said to him, "Even if it is at midday?" He said, "Even if it is at midday."