The reason for the “sandwich”
The Gemara in Pesachim (115a) brings a dispute of tanna’im about the question of how the observance of eating matza and maror took place when the Temple still stood. According to the Sages, one must eat the matza by itself and the maror by itself, whereas Hillel would wrap the matza and the maror and eat them together, as the verse states, “They shall eat it with matzot and bitter herbs” (Bemidbar 9:11). According to the Rambam (Hilkhot Chametz u-Matza 8:6-7), Hillel would wrap only the matza and the maror, whereas according to Rashi and the Rashbam (ibid.) Hillel would wrap the matza and the maror with the Pesach sacrifice and eat them together.
According to Hillel, would failure to eat the items together mean that one has not fulfilled the commandment?
The Rishonim differ as to whether failure to eat the different components together means that one has not performed the commandment according to Hillel.
The Rashbam (ibid.), Ramban (Milchemet Hashem, 25, in the Rif’s pagination) and Rav Yehonatan of Lunil (ibid.) are of the opinion that according to Hillel, a failure to eat the components together means that one has not fulfilled his obligation, and thus one who eats matza, maror, and the Pesach sacrifice separately has not fulfilled his obligation.
On the other hand, according to Tosafot (s.v. ella amar), “Ideally one should wrap them together, but if he did not do so, he has still fulfilled his obligation.” That is also the view of the Ba’al ha-Ma’or (25a, in the Rif’s pagination), that even according to Hillel, a person who eats the components separately has fulfilled his obligation.
According to the Sages, if one eats the components together, has he nevertheless fulfilled his obligation?
The Rishonim also differ as to what the Sages’ position is if a person ate matza and maror together.
Rashbam (ibid., s.v. ve-hashta) understood that Rabbi Yochanan’s opinion in the Gemara there is that if the matza and maror are eaten together, according to the Sages one has not fulfilled his obligation, and that is also the view of the Me’iri and Ba’al ha-Ma’or (ibid.).
On the other hand, the Rashbam understood that Rav Ashi’s view there is that according to the Sages it does not make a difference, and one can fulfill the obligations of matza and maror whether eating them together or separately. That is the view of the Ramban (Milchemet Hashem, there), even regarding Rabbi Yochanan’s understanding.
Explanation of our custom today
The Gemara rules that:
Now that the law was not determined as either according to Hillel or the Sages, one recites [the] “al akhilat matza” [blessing] and eats it [the matza], then recites [the] “al akhilat maror” [blessing] and eats it [the maror], and then eats matza together with Romaine lettuce without a blessing – a remembrance of the Temple practice according to Hillel. In other words, as there was no decision made regarding this dispute, one eats matza by itself, maror by itself, and then matza together with maror. Why do we act that way?
First, we should note, that in our times even Hillel would agree that in order to fulfill the commandment of eating matza, one must eat it by itself. The reason for this is explained in the Gemara (ibid.) that in our times eating matza is a Torah commandment, whereas eating maror is by rabbinic decree, and one is not to mix a Torah commandment with a rabbinic decree, for the taste of the rabbinic decree would nullify the taste of the Torah commandment.