Amir ul Mu'mineen ‘Ali (‘a) said: "Do not become obstinate (and do not strictly follow your own ideas), because such a one will meet destruction."
Tasnif Ghurar-ul-Hikam, p. 443
Imam Amir ul Mu'mineen (‘a) said: "He who considers himself a great one (self-conceited), is naught with Allah.
Tasnif Ghurar-ul-Hikam, p. 308 & Bihar-ul-Anwar, vol. 6, p. 91
Imam Amir ul Mu'mineen ‘Ali (‘a) said: "Two things cause people to be destroyed (and lead unto Hell): fear of poverty, and seeking superiority through pride."
Bihar-ul-Anwar, vol. 72, p. 39
Imam Amir ul Mu'mineen ‘Ali (‘a) said: "You should avoid self-admiration, having reliance upon what appears good in yourself, and love of exaggerated praise because this is one of the most reliable opportunities for Satan."
Ghurar-ul-Hikam, p. 298
Imam as-Sadiq (‘a) said: "He who has even a little arrogance in his heart will not be allowed to enter Heaven."
Al-Kafi, vol. 2, p. 310