Musnad Ahmad 30:1660

Al-Khuza'i narrated to us, he said: Ibn Bilal informed us, from Ibn 'Ajlan, from 'Ubayd Allah ibn Salman al-Aghar, from his father, from Abu Hurayrah, that the Prophet, may Allah bless him and grant him peace, said: "It is not befitting for the two-faced person to be trustworthy."