We have to root out from the inner recesses of our souls the deadly poison of anger. For so long as anger remains in our hearts and blinds the eye of the mind with baleful darkness, we shall never be able either to acquire the judgment of prudence or the insight of right contemplation, or ripeness of counsel, nor can we participate in life, nor lay hold on justice, or even be able to receive spiritual and true light…we shall not, again, be able to share in wisdom, although we may appear to be held wise in all men’s estimation, for ‘anger rests in the bosom of a fool’ (Ecclesiastes 7:10)….
We have heard of some who attempt to excuse this most deadly disease of the soul…they say that anger does no harm if we are angry with erring brothers, alleging that God Himself is said to rage and be wrathful against those who refuse to know Him…not perceiving that, while they wish to allow to man the occasion of a deadly sin, they are introducing into the Divine immensity…the evil of a carnal passion…when we read of the anger or of the wrath of God, we must not understand [this] after the manner of our unworthy human passions, but in a sense worthy of God, Who is far removed from our unquiet passions.
~St John Cassian
Prayerful Life 