Musnad Abu Ya'la al-Mawsili 152:221

Abu Khaythama narrated to us, Yazid bin Harun narrated to us, al-Hajjaj bin Artah narrated to us, from Fudayl, from Ibrahim, from Alqama, from Abdullah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "He shall not enter Paradise who has in his heart the weight of a mustard seed of pride."