Institutio Oratoria

But he must put away from him two kinds of pretentious display, the one consisting in the officious proffering of his services to the powerful against those of meaner position, and the other, which is even more obtrusive, in deliberately supporting inferiors against those of high degree. For a case is not rendered either just or the reverse by the social position of the parties engaged. Nor, again, will a sense of shame deter him from throwing over a case which he has undertaken in the belief that it had justice on its side, but which his study of the facts has shown to be unjust, although before doing so he should give his client his true opinion on the case.