Question: [Monday, 28th Sivan, 5782]
In light of the recent article you wrote regarding if one eats only a small amount of bread by a meal, and if it exempts the other meal foods, I have a general question that has bothered me for quite a while. I believe that I have heard that it is forbidden for one to purposely eat less than a Kezayis of bread for the sake of escaping the need to recite Birchas Hamazon. Is this true?
There is no intrinsic Halachic prohibition against one eating less than a Kezayis of bread so he does not have to say Birchas Hamazon, and thus, one may do so if he chooses, so long as it does not enter any of the meal foods into a question of the before blessing [i.e. such as if he is only eating bread, or only eating satiating meal foods with the bread, or is saying an individual blessing on the other foods prior to saying Hamotzi on the bread]. Nonetheless, according to the spirit of the law, it is not appropriate for one to specifically eat less than a Kezayis in order to escape Birchas Hamazon. However, he may do so for other reasons such as he is on a diet, or does not have an appetite to eat more, and the like.
It is a clear ruling in the Talmud and Poskim that an after blessing for the eating of a food is only recited if he ate a Kezayis within Kdei Achilas Peras, and if he eats less than this amount than an after blessing is not said. No mention is ever made of there being an issue with eating less than the above amount, and the Torah and Sages do not dictate how much one should eat, but rather simply state what the law is regarding if one eats such and such amount. Accordingly, there is intrinsically nothing wrong with eating less than a Kezayis of a food even if the intent is to escape the after blessing. Nonetheless, according to some Poskim, if one eats less than a Kezayis of bread then it does not exempt any of the meal foods, and hence it is best to be avoided, or choose from one of the above-mentioned options to circumvent this issue. Now, the above is all according to the letter of the law, however according to the spirit of the law it is never proper for one to purposely try to escape a mitzvah. So is clearly implied from the law regarding Hafrashas Challah, in which it states that one is forbidden from purposely making a batch of dough of less than Shiur Challah in order to circumvent the obligation of separating Challah from it. So is likewise implied from the ruling regarding wearing Tzitzis, that although one is not obligated to wear a four cornered garment to become obligated in Tzitzis, if he does not wear it, he gets punished in a time of anger. Thus, despite the lack of prohibition, it is indeed improper for one to purposely eat less than a Kezayis to escape saying Birchas Hamazon, unless there are mitigating circumstances.
Sources: See regarding prohibition to make less than Shiur Challah in order to exempt from Challah: Admur 456:3; 457:17; Michaber Y.D. 324:14; Rambam Bikkurim 6:16; Yerushalmi Challah 3:1; Pesachim 48b; Shach 324:25; Taz 324:17; See regarding the Mitzvah of Tzitzis: Menachos 41a, stated to Rav Ketina by an angel; Rokeiach 361 “Since one is punished for not wearing Tzitzis therefore everyone must do so.” Tosafus Pesachim 113b “One is punished for not purchasing Tzitzis and making himself obligated in it”; Admur in Hilchos Talmud Torah 3 KU”A 1 “The punishment for nullifying a Mitzvah even though one is exempt, such as Tzitzis.” However see Rashi ibid and other Rishonim ibid that explain that only when one goes out of his way [Tatzdiki] to avoid the Mitzvah of Tzitzis is he punished and not when the chance is simply not readily available. The Ashel Avraham Butchach 21 explains that the punishment mentioned in the Menachos 41 only refers to one who nullifies the Mitzvah constantly. However one who usually fulfills the Mitzvah, and on occasion does not do so, is not included within the punishment. Certainly then one who does not wear a pair of Tzitzis at night has done nothing wrong and will not be punished. [ibid]