Vibhishana did not approve of the killing of Hanuman, who had declared that he was an envoy (of Sri Rama) when the wicked Ravana ordered his murder. [5-52-2]
Then Vibhishana, who was skilled in speech having decided about his duty addressed his reverential elder brother, a conqueror of enemies in soothing, words in a meaningful, wholesome manner. [5-52-4]
'O king of ogres give up your wrath, forgive and calm down. Please listen to my appeal. You know the basic values of life. Virtuous rulers of the earth do not order killing of an envoy. [5-52-5]