Seneca, De Clementia 8
“Think over this as well that, while endurance of what has already occurred exposes private citizens to the danger of receiving additional injuries, greater safety comes to kings from lenience because frequent punishments serve to suppress the hatred of a few while exciting the anger of every one.
The willingness to rage should be weaker than its cause. If not, just as trees which are pruned sprout again with even more branches and as many other plants are cut back so that they may grow more thickly, in the same way a king’s cruelty increases the number of his enemies by cutting some of them down. For the parents and children of those who were killed along with their relatives and friends take up the place of a single victim.”
Adice nunc, quod privatos homines ad accipiendas iniurias opportuniores acceptarum patientia facit, regibus certior est ex mansuetudine securitas, quia frequens vindicta paucorum odium opprimit, omnium irritat. Voluntas oportet ante saeviendi quam causa deficiat; alioqui, quemadmodum praecisae arbores plurimis ramis repullulant et multa satorum genera, ut densiora surgant, reciduntur, ita regia crudelitas auget inimicorum numerum tollendo; parentes enim liberique eorum, qui interfecti sunt, et propinqui et amici in locum singulorum succedunt.