“כבד את אביך ואת אמך”
There is a mitzvah from the Torah to honor your parents. The רמב”ם (הלכות ממרים ו’,א’) writes “והיא מצות עשה גדולה” – it is a great mitzvah. At the same time the ירושלמי (ריש פאה) calls it מצוה חמורה שבחמורות. The פלא יועץ bemoans the fact that people are so diligent when it comes to חיבוב המצוה. They are willing to spend an exobitant amount of money to open the aron for a segula, or to be the sandek. However they are not extra careful when it comes to the מצוה דאורייתא of honoring one’s parents. Every time one listens to his parents, he is fulfilling a מצוה דאורייתא.
We will discuss the halacha of listening to your parents when it conflicts with serving Hashem. There are four categories where this problem arises (1) halacha and הידור מצוה (2) זריזין מקדימין למצוות (3) stringencies in halacha (3) minhagim.
The מחבר (יו”ד סימן ר”מ סעיף ט”ו) rules that one should not listen to his parents if they tell him to transgress a mitzvah, even if that mitzvah is only מדרבנן. The פתחי תשובה (סק”כ”ב) brings from the חמודי דניאל that this applies even to הידור מצוה. If the son feels he will have more kavanah if he davens in a different shul, he may do so even if his parents told him not to.
The halacha of the מחבר only applies if the father told him to transgress a מצוה חיובית – a mitzvah that the son is obligated to do. However if it is only a מצוה קיומית – a mitzvah that one is not obligated to do, then he must listen to his father. This is true as long as the father is not telling him this in order to be מזלזל in mitzvos.
The poskim discuss if כיבוד אב ואם applies to זריזין מקדימין למצוות. For example; someone is making a bris and his parents can only participate if it is done after chatzos. On this R’ Elyashiv zt”l rules that זריזין מקדימין does not override the mitzvah of כיבוד אב ואם and the bris should be made after חצות.
Many poskim including R’ Elyashiv zt”l are of the opinion that even if his father tells him to be מבטל a חומרא he does not have to listen. This is true as long as the חומרא has some source in the poskim, who hold that it is prohibited according to halacha. For example; the חומרא not to carry at all on Shabbos even when inside the Eiruv, or not to cut the beard with a machine or scissors. Or regarding kashrus for food, or being careful about טבילת עזרא. In this regard they are all considered מצוה מדרבנן. Other poskim disagree and כיבוד אב ואם takes precedence over a חומרא. This seems to be the opinion of Reb Shlomo Zalman, and R’ Yaakov Fisher zt”l.
Another topic is if the father tells his son to be מבטל a מנהג. There are three categories of מנהגים (1) A מנהג קבוע that has sources from chazal and is brought in the poskim and everyone in Klal Yisroel practices it, for example; Hallel on Rosh Chodesh. One may not listen to his father to be מבטל this מנהג. (2) A מנהג which is brought in the poskim but does not have a source from chazal, for example saying kaddish for a parent or the minhag of kapparos. Or a minhag that is not practiced by all of Klal Yisroel. The ים של שלמה holds one should not listen to his parents to be מבטל this minhag. If a father tells his son not to say kaddish for the mother since he is still alive, he may not listen. The חיד”א disagrees, since it is not mentioned in Chazal, one must obey his parents. (3) A מנהג or מילי דחסידותא which is not brought in the poskim. For example; going to the mikvah for תוספת קדושה, the length of the peyos and certain minhagim with regard to clothing.
If the reason the father is telling his son not to do the חומרא or מנהג is for no other reason than to be מזלזל in the mitzvos, the son should not listen to his father.
Prepared by R’ Avrohom Yehoshua Ziskind
 Sources:פסקים ותשובות,פלא יועץ