There is a well-known Gemara in Pesochim (109b) which discusses the danger of doing things in pairs. At a sheva berachos for a son of my Rosh Yeshiva, R’ Tzvi Kaplan shlita, I heard one of the darshonim ask why we aren’t worried about this when it comes to a chosson and kallah. At the time I thought it was a joke question, but since then I have seen that the Iyun Ya’akov actually asks the question.
Below are a number of answers:
1) The Gemara in Sotah (17a) teaches: איש ואשה זכו שכינה שרויה בניהם – “If a husband and wife are meritorious, the Shechinah will rest in their midst” When a husband and wife act the way they should, the Shechinah rests in their midst. Consequently, when they get married there is actually three people not two, therefore, there is no problem of zugos. (Iyun Ya’akov)
The Gemara in Kesubos (17a) says: רב שמואל בר יצחק מרקד אתלת – “Rav Shmuel bar Yitzchok would dance with three”. Rashi explains, he would dance with three hadasim [myrtles]. The Maharsha asks, that the Gemara should have said בתלת – “with three”, not אתלת – “on three”. According to the above, we can explain, that Rav Shmuel bar Yitzchok wouldn’t dance at every chasunah – he would only dance at a chasunah which brought with it hashro’as Shechinah. I.e. he would only dance אתלת, at a chasunah where there was three, the chosson, kallah and the Shechinah. (This peshat I saw brought down from R’ Yitzchok Shmuel Shvartz in Madanay Asher)
Based on the above we can understand the Chazal which says: דאם לא זכו אש אוכלתן – “that if they aren’t meritorious, they will be consumed by fire”. Since the only reason there is no problem of zugos is because the Shechinah rests amongst them, if they get into fights, they cause the Shechinah to leave, and then there is in fact a problem of zugos.
2) The Zohar (Parshas Vayikra) says, that before a chosson and kallah get married they are פלג גופא – “two halves of a whole”, once they get married, they become one (והיו לבשר אחד). According to the Zohar, when a chosson and kallah get married they become one, since they are one, there is no problem of zugos. (Iyun Ya’akov)
3) R’ Shamai Gross shlita answers, that zugos is a problem when one person uses two items. Here, however, the husband uses his wife, and she uses him. Each one uses the other, however, both husband and wife are only using one item.
According to the above, for one man to have two wives would be problematic. R’ Gross suggests, that perhaps it is for this very reason that Rabbeinu Gershom enacted that a man shouldn’t marry two women.
4) The Gemara in Pesochim (110b) which discusses zugos concludes: למאן דלא מקפיד אינו מזיק – “if one is not particular about zugos then he won’t be harmed”. Therefore, when it comes to marriage, as long as each partner isn’t so makpid [particular] about what the other one does, there will be no issue of zugos. (Madanay Asher)
