Question:
The Torah commands that when a married man dies without children, his brother should marry the widow through Yibum (levirate marriage). If so, why is Yibum generally not performed today, and why do we instead perform Chalitzah?
Answer:
The answer depends on whether we are discussing the original Torah law or current practice. According to the Torah, the mitzvah of Yibum remains in effect. Indeed, many Rishonim, including the Rif and Rambam, rule that the mitzvah of Yibum takes precedence over Chalitzah, and this was also the ruling of Maran the Mechaber.
However, other authorities, led by Rabbeinu Tam and the Ashkenazic tradition, ruled that Chalitzah takes precedence. Their concern is based on the opinion in the Talmud of Abba Shaul that Yibum should be performed only when motivated by the mitzvah. If the brother’s intent is motivated by beauty, personal desire, or other interests, the act is viewed with great severity. The Rama therefore records that even if both parties desire Yibum, they are generally not permitted to proceed with it.
Beyond this classical debate, an additional concern developed in modern times. A number of authorities raised the possibility that due to contemporary moral realities, one cannot always be absolutely certain that the deceased truly left no offspring. If a child exists, then the widow is not subject to Yibum at all, and relations with her would constitute the severe prohibition of a brother’s wife. This concern was publicized by Rav Tzvi Hirsch Chajes (Maharatz Chajes), who wrote that this was one of the reasons Yibum ceased to be practiced in modern times.
Practically, the decisive turning point came in the State of Israel. In 1950, the Chief Rabbinate of Israel enacted a nationwide regulation prohibiting Yibum for all communities, including Sephardim who traditionally followed the ruling that Yibum takes precedence. The Rabbinate explained that in contemporary times it is evident that most people do not perform Yibum solely for the sake of the mitzvah, and for the sake of uniformity and communal harmony throughout Israel, Chalitzah alone would be performed.
The enactment did allow for rare exceptions under special circumstances and with the explicit approval of the Chief Rabbinate. Indeed, there was a unique case in which a Sephardic couple sought permission to perform Yibum, and the matter was discussed extensively by the rabbinical courts and ultimately approved by Rabbi Mordechai Eliyahu, then Chief Rabbi of Israel, under the special provisions of the regulation.
Accordingly, although the mitzvah of Yibum still exists in principle, the accepted practice today throughout the Jewish world is to perform Chalitzah rather than Yibum, and Yibum is only considered in the most exceptional circumstances with special rabbinic authorization.
Sources:
Rama E.H. 165:1; Tur 165; Tosafus Yevamos 39b and Kesubos 64a that we rule like Aba Shaul; Abba Shaul Yevamos 39b and Stam Mishneh Bechoros 13a; Rashi Yevamos 39b; Rosh Kesubos 5:36; Maharam Padwa 18; Shut Beis Yosef 2 that so is Minhag Ashkenaz to not perform Yibum ever, only Chalitza; Aruch Hashulchan E.H. 165:15 1950 enactment of the Chief Rabbinate of Israel brought in Heichal Yitzchak E.H. 5; Other opinion: Rif Yevamos 13a; Rambam Yibum 1:2; Chachamim in Yevamos 39b; Rivash 509; Maharatz Chayes to Yevamos 22b; Yabia Omer 6:14-6