Musonius Rufus · Fragments
Fragment 41
To share the common notion that we shall be despised by others if in every way we do not strive to harm the first enemies we meet is the mark of mean-minded and ignorant men. For we say that the despicable man is recognized among other things by his inability to harm his enemies, but actually he is much more easily recognized by his inability to help them.
Musonius Rufus, Lectures and Fragments, Fragment 41, translated by Cora E. Lutz (1947). The Stoic Library.