For the longest time, I really struggled with the part of the Sermon of the Mount that said that to be angry is the same thing as to murder them, and to lust after someone is the same thing as committing adultery. No way is thinking about something the same thing as doing it!
But the question becomes- the same thing for who? While internalizing anger or lust might not create the same experience for the object of those emotions, it can do the same type of harm to the person harboring those feelings.
In Jesus’ mind, to hold on to emotions like anger or lust was as harmful to your soul as committing murder or adultery. Your thought life shapes your character and ultimately directs your actions.
Greek word for anger here is orgizomenos. It means to harbor and contemplate deliberate hostile vengeance. Unresolved anger can eventually lead to destructive actions that multiply the original offense. In Matthew 5, Jesus mentions that your anger can lead you to murder people with your words. It can also manifest itself in other destructive ways. In the process, the person acting out in anger is only re-injuring their own soul.
The Stoics held to the idea that to inflict harm on another person was to inflict harm on yourself. Marcus Aurelius wrote: "To harm is to do yourself harm. To do an injustice is to do yourself an injustice- it degrades you." That's why revenge makes no sense. In seeking the other's harm you'd only harm yourself again.
That's not to say that there isn't such a thing as righteous anger or the pursuit of justice. In fact, some translation of this Matthew passage add "if anyone is angry at their brother without cause." There are times when anger is justified, and action fueled by anger can lead to justice or reconciliation.
But to hold on to deliberate, hostile vengeance...that's to multiply the original offense and let it fester in your soul. "How much more damage anger and grief do than the things that cause them." -MA
Marcus Aurelius also wrote, "The best revenge is to not be like your enemy." Jesus agrees, and pushes us towards forgiveness, justice, and reconciliation rather than hostile, deliberate vengeance.
(I'll unpack lust/adultery in the same way in the next post)