Musnad Ahmad 32:37

Ziyad ibn al-Rabi' Abu Khidash al-Yashkuri narrated to us, saying: I heard Abu 'Imran al-Jawni saying: I heard Anas ibn Malik saying: "I do not recognize anything today that we were upon during the time of the Messenger of Allah, may Allah bless him and grant him peace." He said: We said to him: "What about the prayer?" He said: "Have you not done regarding the prayer what you have already known?"