Expressing anger in places where anger is not permissible causes one to surpass the limits of Shari‘ah, thereby becoming sinful.

As for becoming angry in places where the Shari‘ah has commanded that one express anger for the sake of Allah Ta‘ala, then though it is permissible and necessary, it is important that one remain within the parameters of Shari‘ah when expressing anger.

Generally, when people become angry, they lose their composure and are unable to maintain the balance of justice. Hence, the anger becomes the means for them committing oppression or transgression. Therefore, Rasulullah (sallallahu ‘alaihi wasallam) advised this Sahaabi not to become angry.