John Cassian, The Institutes VIII.10: Of the sun, of which it is said that it should not go down upon your wrath

And of this sun God clearly makes mention by the prophet, when He says, “But to those that fear my name the sun of righteousness shall arise with healing in His wings.” And this again is said to “go down” at midday on sinners and false prophets, and those who are angry, when the prophet says, “Their sun is gone down at noon.” And at any rate “tropically” the mind, that is the νοῦς or reason, which is fairly called the sun because it looks over all the thoughts and discernings of the heart, should not be put out by the sin of anger: lest when it “goes down” the shadows of disturbance, together with the devil their author, fill all the feelings of our hearts, and, overwhelmed by the shadows of wrath, as in a murky night, we know not what we ought to do. In this sense it is that we have brought forward this passage of the Apostle, handed down to us by the teaching of the elders, because it was needful, even at the risk of a somewhat lengthy discourse, to show how they felt with regard to anger, for they do not permit it even for a moment to effect an entrance into our heart: observing with the utmost care that saying of the gospel: “Whosoever is angry with his brother is in danger of the judgment.” But if it be lawful to be angry up till sunset, the surfeit of our wrath and the vengeance of our anger will be able to give full play to passion and dangerous excitement before that sun inclines towards its setting.