Musannaf Ibn Abi Shayba 3:6335

Ali ibn al-Ja'd narrated to us, he said: Abu Ja'far al-Razi narrated to us, from Layth, from Ghalib, from Muhammad ibn Ali, he said: "If he sits for the duration of the tashahhud then breaks his wudu, his prayer is complete, because not everyone knows how to perform the tashahhud."