What is the meaning of "va'Tis'alaf"?
Rashi #1: It means that she covered her face (so that Yehudah should not recognize her). 1
Rashi #2 (to Shir ha'Shirim 5:14) and Targum Onkelos: She made herself look nice.
Targum Yonasan: It means that she wrapped herself in it (the veil).
Ha'amek Davar: She wrapped a scarf around her neck, but it covered also her face, even at the time of intimacy. Otherwise, Yehudah would have recognized her! 2
This is also how Rashi probably translates it according to the Midrash that he cites later (Refer to 38:15:2:2).
What forces him to say so? Even when Bi'ah is permitted during the day, it is only in a dark room, or he covers with his garment to make it dark (OC 240:11)! Perhaps he means until the time [that it was totally dark and proper] for Bi'ah. (PF)
What does "Pesach Einayim" mean?
Rashi #1: It means (that she sat at) the cross-roads. 1
Rashi #2: It means 'next to the opening of [the tent of] Avraham Avinu' - where everybody tended to look. 2
Seforno: It means a fork in the road (the beginning of two roads). 3
Ha'amek Davar: In these lands there are no inns on the road, only an empty house (with beds) in which no one lives. One who needs lodging overnight stays there.
Sotah 10a #1: "Einayim" is actually the name of a town.
Sotah 10a #2: It means that she gave Einayim (lit. 'eyes,' i.e. answers as to why she would be permitted to Yehudah) to the questions that Yehudah asked her when he accosted her - 'Are you an idolater?' - 'I am a convert (to monotheism).' 'Are you married?' - 'I am single.' 'Did your father accept Kidushin on your behalf?' - 'I am an orphan.' 4 'Are you Tamei (a Nidah)?' - 'I am Tehorah.'
Targum Yonasan: It is where everyone looks. Na'ar Yonasan - Whoever passed by would be bound to see her, predominantly Yehudah, who, she knew, would shortly arrive there.
Mizrachi - i.e. Me'aras ha'Machpelah, where he is buried. Maharsha (to Sotah 10a) - The Gemara connotes that it is the opening of his tent. See also Ba'al ha'Turim.
So that whichever road Yehudah took, he could not avoid seeing her.
What was this exchange about? Refer to 38:14:2.3.
"She sat at 'Pesach Enayim.'" Chazal interpret that she added perspective ('Enayim') to her words, (i.e. she explained why in fact she was permitted to Yehudah). "Yehudah said... 'Perhaps your father accepted Kidushin for you?' She replied, 'I am an orphan'" (Sotah 10a). What was this exchange about?
Gur Aryeh (to 38:15) #1: According to Rashi (to Sotah 10a), it was Tamar's mother and brothers who had married her off in the past (for she was a minor at the time of her marriage), and she could still undo those marriages retroactively through Mi'un. 1 According to that Rashi, this explains why she was not forbidden as his daughter-in-law.
Gur Aryeh (to 38:15) #2: Tamar was explaining why there was no concern that her father had accepted Kidushin on her behalf (making her again a married woman). Due to her previous Nisu'in, she had permanently left her father's Reshus (known as Yesomah b'Chayei ha'Av).
Gur Aryeh (ibid.): Although Tamar was now a Gedolah (refer to 38:7:1.1:1), she could still do Mi'un, because Er had only the original Kidushin mid'Rabanan in mind (and not a new Kidushei Bi'ah); the same was true for Onan's intent with his Yibum. Also see Maharsha (to Sotah ibid). (If Tamar was a minor at the time of her marriage to Er, this is unlike the opinion that she was Shem's daughter - PF). Da'as Zekenim (to 38:26) - She did Mi'un to nullity it retroactively. [We can even say that she was Shem's daughter,] like the opinion that an adult can do Mi'un (That is only for mistaken Kidushin (Yevamos 100b)! - PF) Some say that Tamar was single, for only Bi'ah k'Darkah makes marriage for Bnei Noach. This is wrong. All agree that with a husband, even Lo k'Darkah makes her Be'ulas Ba'al.
Why did Tamar do what she did?
Rashi and Ramban: Because she wanted to have children from Yehudah. 1
Seforno: She intended to draw the attention of Yehudah that he should arrange for her marriage (Yibum) with Shelah, seeing as he had grown-up and was fit to do Yibum with her. 2 This she did by changing out of her widow's clothing - that Yehudah himself had instructed her to wear in the interim. 3
Refer to 38:14:151:1.
Ha'amek Davar: She wanted to ask Yehudah to give her to Shelah.
Seeing as he declined to take her as a wife for Shelah. Gur Aryeh - Rashi does not interpret that her intent was simply to bring about her marriage to Shelah; seeing as she did not do anything towards that goal. All she did was make herself Hefker.
In accordance with his own instructions in 38:11.
"V'Hi Lo Nitenah Lo." Why does the Torah insert the (otherwise superfluous) word "Hi"?
Ohr ha'Chayim: Clearly she was not being given to Shelah. "Hi" hints that she saw through Ru'ach ha'Kodesh that it is not correct that she be given to him as a wife; therefore she did what she did - and succeeded.
Why did Tamar remove her widow's clothing?
Seforno: Refer to 38:14:3:2.
Malbim: She showed that she did not want to do Yibum. Since she was not given to Shelah after he matured, she was therefore exempt. She wanted to talk to Yehudah that he should marry her.
QUESTIONS ON RASHI
Rashi writes: "Va'Tis'alaf - I.e., she concealed her face." Why not explain simply, that she dressed herself with it?
Gur Aryeh: That would go without saying; surely she dressed in other clothing in place of her clothes of mourning. The Pasuk is telling us that she took this additional step of concealing her face, so that Yehudah would not recognize her.
Rashi writes: "She sat at 'Pesach Enayim' - i.e. at the crossroads." Why is a crossroads called 'Pesach Enayim'?
Gur Aryeh: When a traveler reaches a crossroads, he must 'open his eyes' [i.e. pay attention] as to which road he must take.
Rashi writes: "She sat at 'Pesach Enayim' - ... The Rabbis interpret, [she sat] at the entrance to [the tent of] Avraham Avinu, which all eyes long to see." Why do they interpret this way?
Gur Aryeh: If it simply means a crossroads, the verse should call it 'Pesichas Enayim.' Rather, it literally refers to an entrance.
Rashi writes that she sat at the cross-roads. Even the lowliest prostitute would not do such a thing!
