On the night of the Seder there is a mitzvah m’d’rabanan to drink four cups of wine. Additionally, there is a mitzvah m’d’rabanan to recline at the seder as well. This second mitzvah to recline was instituted to be performed while one eats matzah and drinks the four cups of wine. The Rambam adds that it is praiseworthy to recline while one eats any other food at the Seder as well, with the exception of marror.
The Gemara (Pesachim 108a) says that one must recline only while drinking two out of the four cups of wine. However, there is a machlokes as to which two. One opinion says to recline only during the first two, and another says to recline during the last two. The Gemara concludes that since we are unsure of the halacha, we recline during all four cups.
The Ran there asks why we would rule stringently when this is a mitzvah m’d’rabanan. Generally the halacha is to rule leniently in doubts that arise in a d’Rabanan. Why then does the Gemara rule stringently to recline by all four cups?
The Ran quotes an answer from Rashi that since it is not a big burden we recline during all four cups. We rule leniently only when there is a tircha – burden involved in ruling stringently. The Ran himself answers that in this scenario it doesn’t make sense to rule leniently. This is because both options are equal, how should we select which cups to recline while drinking? One opinion believes it is the first set and another opines that it is the second set. The two options are equal. And if we rule that one need not recline at all during any of the cups, we will have effectively done away with the entire mitzvah of reclining. The halacha that we may rule leniently in mitzvos m’d’Rabanan applies only when the lenient ruling will not abolish the mitzvah entirely.
What if one forgets to recline? Interestingly, the Gemara does not address this scenario. The Rosh (Pesachim 10:20) says that if one eats either the first kezayis of matzah or the kezayis of matzah for the afikomin without reclining he must eat the matzah again while reclining. And if one drinks the first two cups of wine without reclining he must drink them again while reclining. If one forgets to recline while drinking the last two cups the Rosh is unsure whether one should drink them again. The reason why one should not is because one is not permitted to drink after those cups. Therefore, if one was not required to recline while drinking those cups he would have performed his obligation correctly and would not be permitted to drink any additional cups of wine.
It seems that the Ran would disagree with the Rosh about this point. The answer that the Ran quotes from Rashi that we rule leniently because there is not a big tircha – if one forgets to recline requiring him to drink cups of wine again could be considered a tircha. Therefore according to Rashi if one forgot to recline while drinking any of the four cups he would not have to drink them again.
According to the Ran if one did not recline while drinking either the first two cups or the last two cups we would not require that he drink them again. This is because we would rule leniently that he is not required to drink those cups again. This would not abolish the mitzvah in its entirety.
However, if one did not recline during three or four of the cups we would require him to drink them again and recline.
