Be ye angry and sin not (οργιζεσθε κα μη αμαρτανετε). Permissive imperative, not a command to be angry. Prohibition against sinning as the peril in anger. Quotation from Psalm 4:4.

Let not the sun go down upon your wrath (ο ηλιος μη επιδυετω επ παροργισμω). Danger in settled mood of anger. Παροργισμος (provocation), from παροργιζω, to exasperate to anger, occurs only in LXX and here in N.T.