Chapter 80.— 175.  Petilianus said:  "Lastly, what is the justification of persecution?  I ask you, you wretched men, if it so be that you think that your sin rests on any authority of law." 176.  Augustin answered:  He who sins, sins not on the authority of the law, but against the authority of the law.  But since you ask what is the justification of persecution, I ask you in turn whose voice it is that says in the psalm, "Whoso privily slandereth his neighbor, him will I cut off." 2189   Seek therefore the reason or the measure of the persecution, and do not display your gross ignorance by finding fault in general terms with those who persecute the unrighteous. 2189     Ps. ci. 5 .