Quintilian, Institutio Oratoria, Book 6
Harold Edgeworth Butler, Ed.

[28] Much depends on the occasion on which a jest is uttered. For in social gatherings and the intercourse of every day a certain freedom is not unseemly in persons of humble rank, while liveliness is becoming to all. Our jests should never be designed to wound, and we should never make it our ideal to lose a friend sooner than lose a jest. Where the battles of the courts are concerned I am always better pleased when it is possible to indulge in gentle raillery, although it is, of course, permissible to be abusive or bitter in the words we use against our opponents, just as it is permissible to accuse them openly of crime, and to demand the last penalty of the law. But in the courts as elsewhere it is regarded as inhuman to hit a man when he is down, either because he is the innocent victim of misfortune or because such attacks may recoil on those who make them. Consequently, the first points to be taken into consideration are who the speaker is, what is the nature of the case, who is the judge, who is the victim, and what is the character of the remarks that are made.