Yehuda and Tamar, Yibbum, and Yahadut

(1) About that time Judah left his brothers and camped near a certain Adullamite whose name was Hirah. (2) There Judah saw the daughter of a certain Canaanite whose name was Shua, and he married her and cohabited with her. (3) She conceived and bore a son, and he named him Er. (4) She conceived again and bore a son, and named him Onan. (5) Once again she bore a son, and named him Shelah; he was at Chezib when she bore him. (6) Judah got a wife for Er his first-born; her name was Tamar. (7) But Er, Judah’s first-born, was displeasing to the LORD, and the LORD took his life. (8) Then Judah said to Onan, “Join with your brother’s wife and do your duty by her as a brother-in-law, and provide offspring for your brother.” (9) But Onan, knowing that the seed would not count as his, let it go to waste whenever he joined with his brother’s wife, so as not to provide offspring for his brother.

(9) כי לא לו יהיה הזרע, he knew that not he alone would get the credit for performing this act of love for his deceased brother, seeing that part of the merit would go to his older brother seeing he had first fulfilled the commandment of marrying, so that he would share in the merit of having a son sired posthumously through a levirate union with his widow by his younger brother. [I fail to understand how someone who married in order to use sex only as an act of self-gratification can be described as having acquired a merit by the act of marrying. Perhaps gratifying the sex urge only with someone to whom one is married is by itself a מצוה, and this is what Seforno had in mind. Ed.]

(10) What he did was displeasing to the LORD, and He took his life also. (11) Then Judah said to his daughter-in-law Tamar, “Stay as a widow in your father’s house until my son Shelah grows up”—for he thought, “He too might die like his brothers.” So Tamar went to live in her father’s house. (12) A long time afterward, Shua’s daughter, the wife of Judah, died. When his period of mourning was over, Judah went up to Timnah to his sheepshearers, together with his friend Hirah the Adullamite. (13) And Tamar was told, “Your father-in-law is coming up to Timnah for the sheepshearing.” (14) So she took off her widow’s garb, covered her face with a veil, and, wrapping herself up, sat down at the entrance to Enaim, which is on the road to Timnah; for she saw that Shelah was grown up, yet she had not been given to him as a wife. (15) When Judah saw her, he took her for a harlot; for she had covered her face. (16) So he turned aside to her by the road and said, “Here, let me sleep with you”—for he did not know that she was his daughter-in-law. “What,” she asked, “will you pay for sleeping with me?” (17) He replied, “I will send a kid from my flock.” But she said, “You must leave a pledge until you have sent it.” (18) And he said, “What pledge shall I give you?” She replied, “Your seal and cord, and the staff which you carry.” So he gave them to her and slept with her, and she conceived by him. (19) Then she went on her way. She took off her veil and again put on her widow’s garb. (20) Judah sent the kid by his friend the Adullamite, to redeem the pledge from the woman; but he could not find her. (21) He inquired of the people of that town, “Where is the cult prostitute, the one at Enaim, by the road?” But they said, “There has been no prostitute here.” (22) So he returned to Judah and said, “I could not find her; moreover, the townspeople said: There has been no prostitute here.” (23) Judah said, “Let her keep them, lest we become a laughingstock. I did send her this kid, but you did not find her.” (24) About three months later, Judah was told, “Your daughter-in-law Tamar has played the harlot; in fact, she is with child by harlotry.” “Bring her out,” said Judah, “and let her be burned.” (25) As she was being brought out, she sent this message to her father-in-law, “I am with child by the man to whom these belong.” And she added, “Examine these: whose seal and cord and staff are these?” (26) Judah recognized them, and said, “She is more in the right than I, inasmuch as I did not give her to my son Shelah.” And he was not intimate with her again.

The Story ends with Tamar naming and giving birth to twins.

Then Judah said to Onan

Judah was the first to practice Yibum. It was taught if anything was in the category of permitted then it became forbidden and then again permitted. Thus a Yebama (in-law) was in the category of permitted (before she was married) then became forbidden, and once again becomes permitted. Lest you think that she returns to her original permitted state, scripture teaches, "her husbands brother shall go in unto her, as a religious duty".

(5) When brothers dwell together and one of them dies and leaves no son, the wife of the deceased shall not be married to a stranger, outside the family. Her husband’s brother shall unite with her: he shall take her as his wife and perform the levir’s duty.

(7) But if the man does not want to marry his brother’s widow, his brother’s widow shall appear before the elders in the gate and declare, “My husband’s brother refuses to establish a name in Israel for his brother; he will not perform the duty of a levir.” (8) The elders of his town shall then summon him and talk to him. If he insists, saying, “I do not want to marry her,” (9) his brother’s widow shall go up to him in the presence of the elders, pull the sandal off his foot, spit in his face, and make this declaration: Thus shall be done to the man who will not build up his brother’s house! (10) And he shall go in Israel by the name of “the family of the unsandaled one.”

For the yevamah to administer chalitza to her levir if he does not wed her. As the exalted one said "then she shall remove his show from off of his foot" the laws of this Mitzvah have been explained in the tractate devoted to it - Yevamoth. You are familiar with the idea that "The mitzvah of yibum takes precedence to the mitzvah of chalitza" for which reason the tractate is called yevamoth even though it contains the laws pertaining to both yevamoth and chalitza.

Why do we do Yibum with only with a brother and not with a father like it was done with Yehudah and Tamar? If Yibum is with Yehuda like Brit Milah is with Avraham who did it exactly as it was commanded from Hashem than we would without a doubt need to follow in his ways. However, Yehuda organized and created the idea of Yibum by himself according to his knowledge. Even though he established that the closest relative preform Yibum it is not according to this that we act, we act according to what G-s ruled which is to do this only with brothers. As we saw in the Pesukim In Bereshit Above Yehuda said to Onan "Join with your brother’s wife and do your duty by her as a brother-in-law, and provide offspring for your brother". We know that if he would've slept with her it wouldn't have been with the Kavanah of Yibum because he thought she was a prostitute. She did what she did with the right Kavanna but Yehudah's actions were not with the correct Kavannah. If this is so we don't take Yehudah as a proof for the specifics of Yibum. His actual actions were an accident, he didn't mean to do Yibum. Even he commanded Yibum to be done only with a brother his actions were not connected with Yibum. We know he did not sleep with her anymore - if he was doing full yibum he wouldn't have stopped sleeping with her. Rather, he knew that this was accident and Yibum should be done with brothers. According to this, brothers are equal in regards to when one brother dies the other can marry his wife and she will desire him as much as the dead brother. You wouldn't find this with a father because he will be old and bitter that his son died. Brothers are more similar to each other because they have the same genetic material from their mother as well as their father... so there is no question - we do learn Yibum from Yehuda just differently from what we might have expected.

(28) God blessed them and God said to them, “Be fertile and increase, fill the earth and master it; and rule the fish of the sea, the birds of the sky, and all the living things that creep on earth.”

(1) Every man is obligated to marry a woman in order to be fruitful, and to multiply and anyone who doesn't engage in being fruitful and multiplying is as if he spills blood, and lessens the appearance, and causes the divine presence to depart from Israel.