With regard to wearing tefillin on chol hamoed (intermediate days of the festivals) the Shulchan Aruch (Code of Jewish Law) states (OC 31:2):
“On Chol HaMoed it is prohibited to wear tefillin for the same reason as on shabbat or a holiday, namely that Chol HaMoed is an ot, a “sign” (rendering tefillin, which is also a “sign,” superfluous).” The Ram”a, Rabbi Moshe Isserless, (who records the Ashkenazic custom) adds: “There are those who maintain that one is obligated to wear tefillin on chol hamoed and the custom in all these regions is to put on tefillin with a beracha. The only difference is that the beracha is not recited out loud in shul as is normally done.”
The Mishnah Berurah comments:
“…Many latter authorities write that it is not correct in one minyan for some to wear tefillin on chol hamoed and some not to, for this violates the negative command of “lo titgodidu” (the principle that it is improper to appear as if the Jewish people are divided and in disagreement). Additionally one who does not wear tefillin on chol hamoed and prays in a minyan where the custom is to wear them, should also wear them, but without a blessing. A congregation whose custom is to wear tefillin on chol hamoed should not change their custom.”
When I tell people about this halacha, that a shul should not have some people who are wearing tefillin on chol hamoed and some who are not since it would create the appearance that the Jewish people disagree with each other and are divided into groups, they laugh. The reason for their laughter is obvious, for, we are in so many ways a divided people. Even within Orthodoxy, we are right, left, and middle; Ashkenaz and Sefard; modern, haredi and chassidish; -we seem anything but unified and conforming. And yet, this principal of lo titgodidu, of retaining the appearance (and by extension reality?) of unity, seems here to be not only an abstract principle but a serious halachic one, whose source is a Biblical verse:
בָּנִ֣ים אַתֶּ֔ם לַֽיהוָ֖ה אֱלֹהֵיכֶ֑ם לֹ֣א תִתְגֹּֽדְד֗וּ וְלֹֽא־תָשִׂ֧ימוּ קָרְחָ֛ה בֵּ֥ין עֵינֵיכֶ֖ם לָמֵֽת׃
You are children of the LORD your God. You shall not cut yourselves or shave the front of your heads because of (in mourning of) the dead. -Deuteronomy, 14:1
Reish Lakish said to Rabbi Yoḥanan: I read here the verse: “You shall not cut yourselves [titgodedu]” (Deuteronomy 14:1), which is interpreted as meaning: Do not become many factions [agudot]….
“You shall not cut yourselves”(Deuteronomy 14:1), which is interpreted to mean: Do not become numerous factions. Abaye said: When we say that the prohibition: “You shall not cut yourselves” (i.e. divide yourself into groups) applies, we are referring to a case where two courts are located in one city, and these rule in accordance with the statement of Beit Shammai and those rule in accordance with the statement of Beit Hillel. However, with regard to two courts located in two different cities, we have no problem with it. (Talmud Yevamot, 13b-14a)
The talmud above is interpreting the double meaning of the word titgodidu. Though it means “to cut,” it can also mean “a group (agudah)”. Thus rendering the verse: “Do not divide into groups.” The Talmud concludes based on this that it is forbidden for two courts in one city to hold two different practices.
Though it is true that the Jewish people are divided, and often I see this as a point of strength, for as we are creative, argumentative, independant, and bring more to the world and to each other by not being the same, by the same token, I am very glad there is such a halacha as “lo titgodidu.” At least the principal exits and, in its limited way, has some power to govern our actions and impact our values. If we take lo titgodidu seriously I think it can be part of an important synergy and dialectical tension for us. We will not all agree, but at least in certain circumscribed areas of halcha we can practice, appear, and feel for a brief moment, as if we do.
In light of this halacha and the, at least theoretical, unification it can facilitate, I think the direction many modern Orthodox synagogues have taken in regard to this issue is dangerous. Due to several sociological and historical factors (among them that more young people studying in Israel for a year or two where the universal custom is not to wear tefillin on chol hamoed, and the proliferation of Chabad whose custom is not to wear tefillin on chol hamoed) more and more synagogues which are fully Ashkenazic, and in which 40 years ago all members wore tefillin, are quickly becoming places in which 80%-90% of attendees on a given chol hamoed morning are not wearing tefillin while only 10%-20% are.
Many rabbis have chosen to ignore this phenomenon, and deem lo titgodidu not worth the effort of putting their halachic foot down. But I think we must. At the same time the Mishnah Berurah’s method of forcing everyone to wear tefillin in synagogues where that is the custom, can not work. If we attempt to force those who do not wear tefillin to wear it, they will respond that we are forcing them to violate the sanctity of the holiday and will not cooperate. On the other hand if we ask tefillin wearers to abstain from wearing tefillin during services on chol hamoed they can still have the option of donning them before or after the service.
And so we are faced with competing values as we often are in halcha. Do we change the custom of the synagogue and ask that no one wear tefillin during the services on chol hamoed, or do we say nothing, as I think many of us are want to do, and violate the principle of lo titgodidu?