Be ye angry, and sin not. Quotation from the Septuagint version of Psalms 4:5. Anger, the feeling and expression of displeasure, is not wholly forbidden, but is guarded by two checks. Our Lord did not make anger a breach of the sixth commandment, but being angry with a brother without cause.
The first check is to beware of sinning; to keep your anger clear of bitterness, spite, malevolence, and all such evil feelings. The second is, Let not the sun go down on your irritation; examine yourself in the evening, and see that you are tranquil.
Eadie quotes Thomas Fuller: "St. Paul saith, 'Let not the sun go down upon your wrath,' to carry news to the antipodes in another world of thy revengeful nature. Yet let us take the apostle's meaning rather than his words—with all possible speed to depose our passion; not understanding him so literally that we may take leave to be angry till sunset; then might our wrath lengthen with the days, and men in Greenland, where day lasts above a quarter of a year, have plentiful scope of revenge.
And as the English, by command of William the Conqueror, always raked up their fire, and put out their candles when the curfew bell was rung, let us then also quench all sparks of anger and heat of passion."
It is especially becoming in men, when about to sleep the sleep of death, to see that they are in peace and charity with all men; it were seemly always to fall asleep in the same temper.