Musnad Ahmad 938:47

Waki’ narrated to us, Kathir bin Zayd narrated to us, from al-Muttalib bin Abdullah, from Zayd bin Thabit: That he was asked about the recitation in the Dhuhr and ‘Asr prayers? He said: "The Messenger of Allah, may Allah bless him and grant him peace, used to lengthen the standing, and he would move his lips."