Continuing from yesterday’s post, we left off with a question of why if you missed drinking a cup b’haseiba we do not apply the principle of safeik derabbanan l’kula according to some Rishonim and excuse you from redrinking. The Bais HaLevi points to a gemara in Beitza that sheds some light on the issue. The gemara (Beitza 14) offers two reason why grinding salt on Yom Tov must be done with a shinuy, but grinding spices not: 1) all dishes require salt and it could have been ground the day before; not all dishes need spice and one could not anticipate the need; 2) spice loses its flavor if left standing after being ground; salt does not. There are practical differences between these views: what if one knows in advance that one is cooking a dish that needs spices (according to reason #1, the spice would have to be ground in advance; according to reason #2 not), or what if one is working with a sharp spice that does not lose its flavor (according to reason #1 it still can be ground on Yom Tov as its use was unanticipated; according to reason #2 it must be ground in advance)? Tosfos paskens that we are machmir in both of these cases and require the spice be ground in advance. We do not apply the rule of sfeika derabbanan l’kula here because each reason carries with it both a kula and a chumra – knowing the dish in advance creates a chumra according to reason #1 but a kula according to reason #2, using a sharp spice creates a kula according to reason #1 but a chumra according to reason #2. Either reason is as much a chumra as a kula! What is interesting, notes the Bais HaLevi, is that even the Ran subscribes to this reasoning of Tosfos.
Returning to the case of 4 kosos, the gemara had two versions of R’ Nachmans statement: the first version requires haseiba in the first 2 kosos but not the last 2; the second version requires haseiba in the last 2 kosos but not the first 2. Each version of R’ Nachman’s statement carries with it a kula regarding 2 cups, and a chumra regarding 2 cups. Shouldn’t this case be identical to the case in Beitzah!? In fact, says the Bais haLevi, this is perhaps why Tosfos and Rosh disagree with the Ran and do not consider sefeika derbbanan l’kula here and require haseiba l'ikuva by all 4 cups!
Hopefully this has not been too confusing, because now we are back to square one. Tosfos equated the sugyos in Beitzah and Pesachim and did not apply sefeka derbbanan l’kula in either one. The Ran, however, adopted Tosfos' opinion with respect to the sugya in Beitzah regarding grinding spices, but in Pesachim, even though each statement of R' Nachman is both a kula and a chumra combined, the Ran is bothered why the gemara does not use the the rule of sefeika derabbanan l’kula to reject both statements. Clearly, the Ran saw some difference between the two sugyos. Homework question for Shabbos is to figure out what that difference is...
(if you want to see this inside - Bais HaLevi vol 3, 1:9)