Surah 7. Al-A'raf, Ayah 200

I.e., anger at the rejection of the truth by "those who choose to remain ignorant". The words "to blind anger" interpolated between brackets are based on a Tradition according to which the Prophet, after the revelation of the preceding verse calling for forbearance, exclaimed, "And what about [justified] anger, O my Sustainer?" - whereupon the above verse was revealed to him (Tabari, Zamakhshari, Razi, Ibn Kathir).

Even a Prophet of Allah is but human. He might think that revenge or retaliation, or a little tactful silence when evil stalks abroad, or some compromise with ignorance, might be best for the cause. He is to reject such suggestions.