Al-Muttalib bin Abdullah (may Allah be pleased with him) relates: The people began to dispute about the recitation in the Zuhr and Asr prayers, so they sent me to Kharijah bin Zayd. He said: Sayyiduna Ubayy bin Ka'b related this: The Prophet (peace and blessings be upon him) used to stand for a long time and move his lips, from which I came to know that this was only because of recitation, so I also do the same.
Ahmad and al-Tabarani (in al-Mu'jam al-Kabir) recorded it; its chain contains Kathir bin Zayd, about whose use as evidence there is disagreement.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2682