Don't hate. That's pretty simple. If you've been reading these essays in sequence you're probably tired of me saying "and that's pretty good advice," but it is. Hate is dysphoric for both giver and receiver, and it frequently gives rise to harm for both giver and receiver.
But since my approach to these precepts is not about setting up a bunch of rules for people to obey, there's something still deeper here. This is the last of the four precepts attending to the personal orientation to the concept of self, and it is a precept, that is, a reminder for when one steps off the path, because it signals the delusion of self-hood. Without a self, harboring ill will for another is impossible. There is no other unless there is a self.
What is meant by "ill will" anyway? "Ill," of course, refers to illness, and "will" refers to intention. "Ill will" is an intention for another to be un-well. For me, it usually arises out of a comparison, or out of a notion that I have been targeted in some way by someone else. In every case, one thing that is necessary for ill will is for me to have identified with the Self, that separately-existing individually-identifiable entity that the buddha-dharma teaches is really a mass social hallucination. Essentially all of my zen practice heretofore has been directed at looking carefully at the Self, and sure enough, the more I look the less substance the notion possesses. So, if I notice ill will arise, I know that I have to some extent bought into the delusion of self. This is really helpful because I can't release this delusion if I don't see it.
Anger goes hand-in-hand with ill will in my life. I can't think of an instance of harboring ill will that wasn't accompanied by anger. But, it is very important to note that they are not the same thing. Anger is a feeling, ill will is a thought. You can't release feelings like you can release thoughts. You can "cure" yourself of a thought. That is, you can see through some notion and dismiss it from your life. Feelings will always revisit you, they are as natural the breath, there's no curing yourself of feelings.
So, what does the buddha-dharma teach you to do with anger? If you express it, you're probably running a real risk of bringing harm. That's no good. If you bottle it up, you're also running a real risk of bringing harm, it may just be later, or you may just harm yourself. Since there's no real difference between harming yourself and harming another (because self and other don't really exist), what do you do? What would Buddha do?
You see it. You metaphorically invite it in for tea, you listen to what it has to say. Anger is always accompanied by energy in my life, so I also try to channel that energy into something useful. What I've noticed in my own life is that anger doesn't really survive being seen. Once anger is seen it begins to disintegrate. If you keep watching it will eventually completely vanish.
It's the difference between "I am angry" and "I feel angry." The former is a delusion, the latter is an observation. When you're angry you haven't changed into something else. You're the same. All that is different is that anger has shown up. Just see it.
That doesn't mean you should accept injustice or become some kind of smiling zombie doormat. Not expressing anger is not the same as not taking action. You know the difference.
Harboring ill will has been, for me, an expression of anger, a failed and ineffective way to remedy some injustice. There's nothing wrong with remedying injustice, in fact, quite the contrary. It is wrong to NOT remedy injustice. The problem here is that harboring ill will just multiplies the injustice. It's like putting out a fire with gasoline.
First, you obscure the truth of whatever is going on from your view with this idea that you have a self that needs to be defended, then to the extent that an action taken in anger cause anger in another you've increased the likelihood that that person can't see what's really going on, either. Pretty soon everyone is just lost in their own drama and confusion reigns the day. You've seen this happen time and time again, I'm sure, probably today even.
This is also exactly how wars start, how murders happen, how every brutality that mankind visits upon itself arises. You really don't have to play, and one really effective way to not play is to pull the entire process up by it's roots while it is still just a nascent sprout of ill will. This precept reminds you of that choice.
Since the self doesn't exist, it doesn't need defense. Anger can then just be seen, and in being seen it evaporates on it's own. Absent persistent anger, ill will does not arise. Therefore, a follower of the Way does not harbor ill will.
Next - A follower of the Way Does not abuse the Three Treasures.