Musnad Ahmad 21:15

Muhammad ibn Idris—meaning al-Shafi‘i—narrated to us, ‘Abd al-‘Aziz ibn Muhammad narrated to us, from Yazid—meaning ibn al-Had—from Muhammad ibn Ibrahim, from ‘Amir ibn Sa‘d, from al-‘Abbas ibn ‘Abd al-Muttalib, that he heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "He has tasted the flavor of faith who is pleased with Allah as Lord, with Islam as a religion, and with Muhammad as a Messenger."