Musannaf Ibn Abi Shayba 17:97

Ali ibn Mushir narrated to us, from al-Shaybani, from al-Walid ibn al-Aizar, from Sa’d ibn Iyas Abu ‘Amr al-Shaybani, from Ibn Mas’ud, who said: I said, "O Messenger of Allah, which of the deeds is best?" He said, "The prayer at its appointed time." I said, "Then what?" He said, "Kindness to parents."