Our Gemara on Amud Beis tells us a clever derash on the verse that describes Yehuda meeting up with the Zonah, who actually was Tamar in disguise. Tamar still wanted to bear children for Yehuda’s family line, and since Yehuda was delaying offering a levirate marriage with Shelah, she took matters into her own hands.

The verse (Bereishis 38:15) states:

וַיִּרְאֶ֣הָ יְהוּדָ֔ה וַֽיַּחְשְׁבֶ֖הָ לְזוֹנָ֑ה כִּ֥י כִסְּתָ֖ה פָּנֶֽיהָ׃

⁦When Judah saw her, he took her for a harlot; for she had covered her face.

The Gemara wonders, “Why would a prostitute be wearing a face covering? And, if so, why would that make Yehuda think she is a prostitute? 

The Gemara reinterprets the subtexts of the verse. Since Tamar was so modest in her father in law’s home and always covered herself, Yehuda then did not recognize her now. Since he didn’t recognize her, she was able to fool him into thinking she was a prostitute. In other words, the “covering her face” was not in the present, but rather in the past as she conducted herself back at home. This is a clever way of injecting a lesson of modesty into a story that, on its surface, is not modest. We now can see Tamar as a heroine, who can be modest most all the time, but can go against her grain and behave differently, if she felt the situation required it. The reinterpretation is similar to another Midrash by Avraham, where he declares his concerns about Sarah being noticed by the immoral Egyptians (Bereishis 12:11), “Behold now, you are a beautiful woman.” The simple peshat is, “Now has come the time for us to be concerned about your beauty.” However the Midrash (see Rashi and Sifse Chachamim Ad loc) learns that Avraham and Sarah were so modest that he never focused on her beauty until now. Some say, as they were crossing a river she had to lift her clothes and that’s when he noticed how attractive she was.

But the verse by Tamar has a pashut pshat. Ramban and Rabbenu Bechaye both tell us that indeed prostitutes, at least those in ancient times, did cover their faces partially. This was for two possible reasons. First of all, they did not want their family members to recognize them. Second, because they are performing indecent acts, they hid behind anonymity. Therefore, the pashut Peshat reading of the verse is that she covered her face at the time in the manner that zonahs do, and that he thought her to be a prostitute because of that. 

Though the pashut peshat stands as it is, and is even endorsed by Ramban, it is notable that unlike his usual stance, Ibn Ezra here supports the midrashic interpretation. There is also a historical indication to support the midrashic peshat. We have archeological finds of stone tablets, which are known as the Middle Assyrian Laws. They were written around 600 BCE during the reign of the Babylonian King, Tiglat Paleser, and they discuss rules for prostitutes and their clothing. (Tiglat Paleser is also mentioned in Tanach, Melachim II, chapters 15-16.) In sections 42-106 of these tablets, we find laws that actually punish prostitutes who wear veils. Apparently, there was a concern that they not be confused with respectable married women and mingle amongst them and get away with their activities amongst more decent folk.  Veils were only to be worn by married women.  Thus, there is proof that it was indeed odd for a prostitute to wear a veil, and the Gemara’s question and answer fit well into this.