Musnad Ahmad 32:368

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Hamzah al-Dabbi, from Anas, that he said: "Shall I not tell you a hadith that perhaps Allah will benefit you with? The Messenger of Allah (peace and blessings of Allah be upon him) would not depart when he stopped at a place until he had prayed Dhuhr." Muhammad ibn ‘Amr said: "Even if it were at midday?" He said: "Even if it were at midday."