Rabbi Yehuda HaChassid was born in 1150 and lived in Speyer and later in Regensburg, where he died in 1217. He essentially initiated a school of thought that combines halacha and kabbala, as is evident in many of his writings. He emerged as one of the leading authorities of Ashkenazi Jews of the time and his influence continues to this day.
Rabbi Yehuda HaChassid is probably best known for his Sefer Chassidim, which is a work of ethical, halachic, and kabbalistic teachings. Included in the Sefer Chassidim, though independently famous in its own right, is Rabbi Yehuda HaChassid’s last will and testament. Rabbi Yehuda HaChassid’s will, or tzava’a, contains advice, directives, and rulings on a wide range of issues. Although a number of Rabbi Yehuda HaChassid’s rulings have found their way into the Shulchan Aruch, many of the statements in the tzava’a are quite mysterious and even incomprehensible, which has left rabbinic authorities throughout the ages questioning the logic and authority of such statements. In fact, some of the rulings in the tzava’a contradict explicit Talmudic statements and normative halacha.
One of the problematic rulings in the tzava’a is that a man should not marry his niece. This is in conflict with the Talmud and other authorities, who rule that doing so is actually a mitzvah. Another perplexing ruling is that a father and a son should not marry two sisters. However, the great Talmudic sage Rav Pappa and his son did just that. Of course, if there were anything wrong with doing so Rav Pappa would not have allowed it. A similar such ruling in the tzava’a is that two brothers should not marry two sisters. It is especially mysterious why Rabbi Yehuda would decree such a thing, as it seems to have been commonplace in the Talmudic era. There is a view, however, that all marriage-related bans of Rabbi Yehuda HaChassid were only intended for those who marry for ulterior motives, such as for financial considerations and the like, but those who marry l’shem shamayim are not subject to any concerns or restrictions.
As a result of the difficulties with many of his rulings, it has been widely suggested that Rabbi Yehuda HaChassid wrote the tzava’a specifically for his own family and future descendants to follow and that it was never intended to be observed by the masses. Some even say that the rulings of the tzava’a are null and void in our day and that there is no reason to follow them at all. Additionally, there is a view that the advice and rulings of the tzava’a don’t apply in Eretz Yisrael. There is also an opinion that a talmid chacham is not required to follow the rulings contained in the tzava’a.
Many authorities, however, encourage one to adhere to the tzava’a whenever possible or to at least observe the rulings of the tzava’a that have become somewhat mainstream. For example, Rabbi Yehuda HaChassid’s ban on marrying someone with the same name as one’s parent is something that has been widely observed throughout the ages even though there is no true halachic prohibition against doing so. On the other hand, while it might be ideal to observe Rabbi Yehuda HaChassid’s ban against taking a haircut on Rosh Chodesh, one who is in dire need of a haircut on a Friday that coincides with Rosh Chodesh should not hesitate to get one in honor of Shabbat. Some communities even dismiss the tzava’a entirely, including a number of Chassidic sects. This approach is based on the view that it is improper to forbid that which the Talmud itself explicitly permits. There is also some discussion as to the authenticity of the tzava’a, with some scholars suggesting that the text and its rulings might actually be a forgery.
Nevertheless, Rabbi Yehuda HaChassid’s ban on burying two enemies side by side is cited approvingly in the Shulchan Aruch and, as mentioned, the ban on marrying someone with the same name as a parent has gained widespread acceptance as well. Perhaps the words of the Chatam Sofer best summarize the approach that one should have with regard to mystically based rulings such as Rabbi Yehuda HaChassid’s tzava’a in particular: “One who is worried about these things should worry and one who is not worried about these things should not worry!”
 See for example Rema, YD 11:4, 265:11, and 339:1.
 Tzava’a of Rabbi Yehuda Hachassid 22.
 Yevamot 62b; Sanhedrin 76b.
 Rambam, Hilchot Issurei Biah 2:14; Rema, EH 2:6.
 Tzava’a of Rabbi Yehuda Hachassid 27.
 Ketubot 39b. See Rashi, Ketubot 52b, s.v. “Be.”
 Tzava’a of Rabbi Yehuda Hachassid 25.
 Berachot 44a.
 Nishmat Chaim (New) 3:1–3.
 Noda B’Yehuda, EH 79; Arugot Habosem, YD 118; Beit She’arim, YD 196; Tzemach Tzedek, EH 1:143; Pitchei Teshuva, YD 116:6. It is interesting to note that some of Rabbi Yehuda Hachassid’s most pious and prominent descendants did not follow the tzava’a. See Shem Aryeh, YD 27 and Imrei Aish 60.
 Maharam Mintz 79.
 Chatam Sofer, YD 138; Pitchei Teshuva, YD 116:6, EH 2:107; Mili D’chasiduta (Botchach) 459.
 Ezrat Kohen 5–7.
 Ruach Chaim (Palagi) 62:15.
 Terumat Hadeshen, Pesakim 131; Yosef Ometz 37; Yafeh L’lev, YD 3:240.
 Divrei Chaim, EH 1:7, 8; Yabia Omer, EH 2:7.
 Teshuvot Haradvaz 687; Beit Yosef, OC 493; Maharikash 98.
 Teshuvot V’hanhagot 1:731.
 Teshuvot Rabbi Moshe Provencali 9; Divrei Ze’ev, vol. 19, p. 23; Chatam Sofer, YD 138.
 YD 362:6.
 Tzemach Tzedek, EH 1:143; Yosef Ometz 37:3; Ruach Chaim (Palagi), EH 2:62:13; Divrei Chaim, EH 1:7, 8. For much more on the issue of [not] marrying someone with the same name as a parent see: Birurei Chaim 3:27, n. 18:1, 2, and n. 19. See also Ezrat Kohen 5–7; Orchot Rabbeinu 4:246–47.
 Chatam Sofer, EH 116. His position is clearly based on Pesachim 110b. For more on this approach, see Igrot Moshe, EH 1:4, and Yabia Omer 2:7:13; Avnei Tzedek, EH 10.