Musnad Abu Ya'la al-Mawsili 151:99

Suwayd ibn Sa'id and 'Abd al-Ghaffar narrated to us, they said: 'Ali ibn Mushir narrated to us, from al-A'mash, from Ibrahim, from 'Alqamah, from Ibn Mas'ud, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "No one shall enter Paradise who has in his heart the weight of a mustard seed of pride, and no one shall enter the Fire who has in his heart the weight of a mustard seed of faith."