What is the significance of Yibum (which Yehudah initiated - Ramban)?
Ramban: Yibum is one of the Torah's secrets, connected with reincarnation. In fact, it entails bringing down the Neshamah of one's deceased brother. 1
Ramban: Before the Torah was given, it could be performed by any relative (Yehudah was not Er's brother, but rather his father). It is an act of kindness towards one's deceased relative, and refusing to do so displays cruelty, which explains the Chalitzah ceremony.
What was Yehudah's command to Onan?
Malbim: He should do the Mitzvah of Yibum, and establish seed for his brother, to benefit the soul of the deceased.
Ha'amek Davar: Onan did not want her for a wife. Yehudah said that even so, he should do Yibum, and he may divorce her after one Bi'ah with her. 1
If so, why did Yehudah add, "and establish seed for your brother"? Perhaps he sensed that Tamar would become pregnant from the first Bi'ah, like she did later! (PF)
QUESTIONS ON RASHI
Rashi writes: "'Establish seed' - [That] the child will be called after the deceased (Yikarei Al Shem ha'Mes)." What does this mean? Why was Onan so opposed to the idea?
Gur Aryeh: It does not mean that their child should be named Er, the name of the deceased brother; for why would Onan have cared to such a degree over that? (Ramban) Rather, it was because the Mitzvah of Yibum obligated the marriage of Er's wife to Onan; [the deceased] Er would be the cause of this child, i.e. he would be credited to Er's account. 1 [Onan wanted his children to be of his own doing. 2 ]
Gur Aryeh: Rashi uses the expression "called after the deceased" to paraphrase the Pesukim regarding Yibum (Devarim 25:6; also see Rus 4:5,10). Compare to Seforno (to 38:9).
Gur Aryeh: This is also what the Torah means by, "so as not to give seed to his brother" (38:9); i.e. Onan could not allow any children to come about due to Er.
