Musannaf Ibn Abi Shayba 3:2188

4565. Rawh ibn ‘Ubadah narrated to us, from Zakariyya ibn Abi Ishaq, from ‘Amr ibn Maymun, from Jabir ibn Zayd, who said: If the tashahhud in the two rak'ahs escapes you, do not sit in your rak'ah for the tashahhud; follow the Imam.