Chapter 2, Mishnah 4. This mishnah opens with the words "Hu hayah omer" ("He used to say"), and this is the third teaching attributed to Rabban Gamliel, the son of Rabbi Yehudah HaNasi. Unlike the two previous teachings, where this introduction did not appear, here it does - and as we learned in the previous chapter, "Hu hayah omer" means that he was accustomed to say this regularly. It may be that the two earlier statements, about earning a living and about being wary of the government, he said only once; whereas the statement before us he was in the habit of saying always.
The subject matter is different as well. The previous mishnayos dealt with practical issues: how to balance a person's responsibility to support himself with his spiritual aspirations, and how to handle the needs of the community and dealings with the authorities and the government that oversees him. Here we are dealing with a spiritual matter, and the root of the topic is hashgachah - Divine providence, specifically individual providence.
General providence versus individual providence:
Without going on at excessive length, the basic idea is that the Holy One, blessed is He, runs the world in two ways: general providence - a broad oversight, and individual providence - a detailed, precise oversight. Of course, nothing in the world happens unless the Holy One, blessed is He, wants it to, down to the smallest detail of a blade of grass. But in order to preserve the illusion in which a person lives, the illusion that makes free choice possible, things have to look like a system operating without direct and immediate Divine intervention: laws of nature, laws of economics and laws of history, which generally play out in their usual order.
Every person needs individual providence, and everything that happens to him is the work of the Holy One, blessed is He. But the matter is complex: when the State of Israel is at war, or when there is no rain, everyone suffers. Some suffer more than others, but the good and the wicked suffer alike. This is a kind of general providence - large events that happen to a community, a region or a district, and many people get swept up in them.
Alongside this there exists a separate possibility of individual providence: a private intervention that, as it were, breaks the rules, special concessions, exemptions or protections that individuals may merit. But they have to be worthy of it. Our mishnah says that the way a person becomes worthy is fundamentally measure for measure: if a person takes the interests of the Holy One, blessed is He, to heart and makes them his own interests, then the Holy One, blessed is He, will repay him in kind and will take a special interest in protecting his interests - in what he wants and in what he does not want. This is a central and important point for understanding what a tzaddik is and what his relationship with the Holy One, blessed is He, looks like.
A hundred against a hundred:
The best framework for understanding this mishnah, in my view, is the context of marriage - a marriage of love. My wife has a wonderful line: a marriage is not supposed to be a fifty-fifty split between husband and wife, but a hundred against a hundred. That is, each one gives his entire self to the marriage, and each one does his utmost to make sure the other side is taken care of. This is the best system for each one to receive the most. It means that the husband's highest priority is that his wife be happy, and vice versa. This is the conceptual starting point from which we should approach the mishnah.
"Aseh retzono kirtzonecha":
The mishnah says: "Aseh retzono kirtzonecha, kedei sheya'aseh retzoncha kirtzono" - do His will as though it were your own will, so that He will do your will as though it were His own. The idea is that a person should relate to fulfilling the mitzvos, to the will of Hashem, as what he genuinely wants to do above anything else. This is the hundred-against-a-hundred state of marriage: what the person wants is that Hashem's will be carried out, he wants the honor of Heaven, he wants what Hashem wants. And Hashem always acts measure for measure, relating to a person with the very same coin with which that person related to Him - and therefore He will do your will as though it were His own.
This is not a tautological statement, as if once everything you want is what the Holy One, blessed is He, wants, your will no longer has any meaning and the Holy One, blessed is He, does nothing for you. That is not the intent. A person has his own specific desires and values, which can be entirely aligned with the will of Hashem and nevertheless are not necessarily the will of Hashem itself.
The first part of the mishnah is therefore saying that when a person comes to fulfill his mitzvos he should think: "There is a need here, and I want to give of myself, to give my money and my resources, because this is what the Holy One, blessed is He, wants" - even though, had this not been the will of the Holy One, blessed is He, he would not have spent his money, his time and his resources on that very same thing.
And since a person is of this type, the Holy One, Blessed be He, will repay him measure for measure when he himself wants something. If he is indeed one hundred percent inside Hashem's will, then what he wants will not be something forbidden to him or harmful to him, nor will it be something devoid of spiritual value; and yet it is something unique to him, something that in itself, all else being equal, the Holy One, Blessed be He, would not have brought into existence had this person not wanted it.
Two children are competing for the same place in a school, and one of them is your child.
Everyone will get a kosher esrog, but you are asking specifically for an esrog that is kosher and exceptionally beautiful.
The Holy One, Blessed be He, is "fine" with your child being accepted to the school - but there are other children; He is "fine" with your receiving a kosher esrog - but you do not have to receive the finest one in the city. But if that is your will, and you are a person who fulfills the directive "do His will as your own will," then measure for measure the Holy One, Blessed be He, will make your will His will, and you will merit a special hashgachah peratis: your child will get the attention he needs, or you will find the esrog you asked for, or whatever else you truly wanted.
"Batel retzoncha mipnei retzono":
The Mishnah continues: "Batel retzoncha mipnei retzono, kedei sheyevatel retzon acherim mipnei retzonecha" - nullify your will before His will, so that He will nullify the will of others before your will. Notice: this is not a mirror image of the previous clause, as if to say that if you nullify your will before His, He will nullify His will before yours, for the Holy One, Blessed be He, does not nullify His will before anyone. The will of the Holy One, Blessed be He, is all that there is, and it is what prevails.
On the question of Divine providence and hashgachah peratis and how it operates - a question that goes beyond the scope of our discussion here - an obvious difficulty arises: if two people with free choice want things that contradict one another, and both are acting upon each other, what will be and how does it work? Put differently: if something is not meant to happen to you, it will not happen; but what happens when a person with free choice seeks to do it to you - does he come away clean? That is an open question, and this is not the place to resolve it.
The point of our Mishnah is that when you nullify your will - when you want to do something that is not right and you say, "No, the Holy One, Blessed be He, does not want this, and therefore I do not want it either" - then when another person wants to do you harm, the Holy One, Blessed be He, will not let it happen. He will nullify that person's will, and you will be protected. Again: a special kind of hashgachah peratis, a special kind of protection.
Additional approaches in explaining the Mishnah:
The Bartenura: The first part of the Mishnah is dealing with a far more specific case - spending money. When a person spends money for the sake of fulfilling mitzvos, he should want to do so as though he were serving his own purposes.
Rabbi Chaim of Volozhin in Ruach Chaim: A fascinating approach, continuing the balance between learning and working discussed in the previous Mishnayos - "do His will as your own will" means that a person should learn at least as much as he works.
In summary: These are additional approaches, and they may all be correct, but the primary approach to this Mishnah is that a person must enter his relationship with the Holy One, Blessed be He, on a one hundred for one hundred basis: full commitment, giving everything, and a will that is Hashem's will - the honor of Heaven, that the will of the Holy One, Blessed be He, be fulfilled in this world and that His kingship rule over all. And the promise we receive in return from the Mishnah is: do not worry, the Holy One, Blessed be He, will take care of you. You will not lose out by giving one hundred for one hundred. And so it is in marriage as well: a person who gives one hundred for one hundred to a spouse with good intentions, who devotes himself entirely to caring for his spouse - im yirtzeh Hashem, and where there is good will, he will benefit from it even more; even though he gives himself up completely and gives, it will come back to him many times over.