Musnad Ahmad 5:518

Abdullah narrated to us, Ahmad ibn Muhammad ibn Ayyub narrated to us, Abu Bakr ibn Ayyash narrated to us, from al-A’mash, from Sa’d ibn Ubaydah, from Abu Abd al-Rahman al-Sulami, from Ali, that he said: "When you are narrated a hadith from the Messenger of Allah, may Allah bless him and grant him peace, then assume regarding it that which is most guided, that which is most pious, and that which is most awe-inspiring."