Since I learn now about katan (9 years old) I want to ask something which bother me:
If the reason of the YIBUM is build a house for the brother why - if there is a little brother - we are ready to wait till 9 years old - maybe in the meantime the woman (the widow) will be so eldest that she wont pregnant? Why there is no a way to say that if the brother is less than 9 - she will be PTURA from YIBUM?
We apologize for the late response to your questions.
The answer to this question is the same as the answer to your other question regarding doing Yibum with Bi'ah sh'Lo k'Darkah:
The Torah commands that the act of Yibum be performed in order to fulfill the Mitzvah (Devarim 25:5). It does not require that it be done in such a way that the brother's home be built as a result.
your answer that HAKAMAT ZERA is not the main reason isnt so simple.
A. the MALBIM says that HAKAMAT ZERA is the reason
B. The SFORNO says the same
C. the RAMBAN supports the reason by the fact that EILONIT is not BAT-YIBUM because she cant become pregnant.
so my questions remain - If the reason of the YIBUM is build a house for the brother why - if there is a little brother - we are ready to wait till 9 years old - maybe in the meantime the woman (the widow) will be so old that she wont become pregnant?
also, since the reason of the YIBUM is LIVNOT BAYIT LACHIV how can U'LEKAHA be achieved by SHLO KEDARKA? There is no way to "establish a house" in this way!
Similarly: when the Yavam intended to come upon a Behema -- there is no way to "establish a house" in this way!
Thank you for the reference to the Malbim and others. The Malbim does say that the main purpose of Yibum is to have a child to continue the family of the deceased brother. However, later in his commentary, when he mentions those who are exempt from Yibum, the Malbim clearly writes that Yibum must be done "by those for whom it is possible" to have children. Moreover, the Malbim himself says that the Mitzvah of Yibum is only with the Bi'ah Rishonah (even if she does not become pregnant with that Bi'ah). The explanation for this is as follows:
It is true that the purpose of Yibum is "Hakamas Shem l'Achiv." But that is not the purpose of the act of Bi'as Mitzvah of Yibum. The purpose of the Bi'as Mitzvah of Yibum is to remove the Isur of Eshes Ach, so that it should be possible afterwards for the Yavam to be "Mekim Zera l'Achiv," for having a Mitzvah to do Bi'ah suspends the Isur, and after the Bi'ah is done, he will then be married to his brother's wife. Thus, when the Malbim says that the point is "l'Hakim Zera," that is true, but it does not mean that the Torah forces him to have children with the Yevamah, but rather it allows him to, by giving him the opportunity to be Mekim Zera. Therefore, it makes no difference if that first Bi'ah is b'Ones, or sh'Lo k'Darko, or with a Katan, as long as it is possible afterwards for him to be Mekim Zera, then the purpose of Yibum has been fulfilled, because now (after the first Bi'ah was done) they are able to be Mekim Zera.
The Torah did not want to force someone to be Mekim Zera for his brother, because one is not required to compensate for what might have been his brother's negligence (in delaying from having children). The Torah, though, wants to permit him to have children for his brother, and so the Torah gives the first Bi'ah as a Mitzvah in order for it to be able to be Docheh the Lo Ta'aseh. Afterwards, it is enough to accomplish the goal of the Torah as long as there is the opportunity to be Mekim Zera. The second and subsequent Bi'os were not made a Mitzvah because the Torah did not want to force him. (The only problem is a Seris Adam according to Rebbi Akiva, but Rava answered that question already in the Gemara, 79b).
M. Kornfeld