- Question: What is the Chazon Ish’s psak about one who swears: “I will not eat matzo on the night of Pesach and the seven days of the holiday “?
A. The Shulchan Aruch (Orach Chaim siman 485) says that if one in general swears “I will not eat matzo” he is forbidden to eat matzo on the night of Pesach. If he swears “I will not eat matzo on the first night of Pesach” he gets lashes and must eat matzo on the night of Pesach.
B. The Mishna Berura there says that as a rule if one includes in his oath something that applies to a mitzva and also does not apply to a mitzva, the oath works and he can’t even do the mitzva like in this case if he swears in general to not eat matzo even if he says this on the night of Pesach, since it includes eating matzo in general which is not a mitzva and the night of Pesach which is a mitzva, he still cannot eat matzo even for the mitzva. But in the other case since he specified not eating on the night of Pesach then we can assume he was referring specifically to not wanting to fulfill the mitzva and an oath to not fulfill a mitzva or to transgress a mitzva does not work.
C. The Be’ur Halacha says that if one swears “I will not eat matzo the whole week of Pesach” the oath works according to most poskim, even though Pesach is mentioned explicitly because the oath is inclusive of both matzo to be eaten for non-mitzva and mitzva purposes.
Answer: The Chazon Ish (Orach Chaim 123:2) says that since he separately mentioned the night of Pesach, it is not considered an oath inclusive of permissible (non-mitzva) things, rather it is two separate oaths, one for the night of Pesach and the other for the rest of the holiday and therefore the oath does not work for the night of Pesach and he must eat matzo then for the mitzvah.