Musannaf Ibn Abi Shayba 3:6415

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Kathir ibn Zayd narrated to us, from al-Muttalib ibn ‘Abd Allah ibn Hantab, from Zayd ibn 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 move his lips.