Musannaf Ibn Abi Shayba 3:1402

Sharīk and Jarīr narrated to us, from Mūsā ibn Abī ‘Ā’ishah, from ‘Abd Allāh ibn Shaddād, who said: The Messenger of Allāh (may Allāh bless him and grant him peace) said: "Whoever has an Imām, then his recitation is a recitation for him."