Was it not wrong for Judah to have relations with a woman he thought to be a harlot, as the Bible says that he did?

w73 383-384:  Questions From Readers
● Was it not wrong for Judah to have relations with a woman he thought to be a harlot, as the Bible says that he did?—
In reality, Judah did not have relations with a harlot, but unwittingly took the place of his son Shelah in performing brother-in-law marriage and fathering legal offspring. Consider the background:
After Judah’s second son Onan died in execution of divine judgment, Judah sent his daughter-in-law Tamar back to her father’s home until such time as his third son Shelah was old enough to be united with her. But even after Shelah had grown up, Judah did not give him in marriage to Tamar. So when Judah lost his wife in death, Tamar disguised herself as a prostitute and then seated herself on the road that Judah would be traversing. Not recognizing his daughter-in-law and assuming her to be a prostitute, Judah had relations with her.—Gen. 38:11-18.
Since Tamar was being held in reserve for brother-in-law marriage with his third son Shelah, when Judah learned that Tamar was pregnant he pronounced the judgment of death on her for having prostituted herself. When it came to light that Judah himself had unknowingly made her pregnant, Judah exclaimed: “She is more righteous than I am, [why?] for the reason that I did not give her to Shelah my son.” Judah was not married at the time; he was a widower, and so he was not sinning against a wife of his. And the disguised Tamar he mistook to be an unmarried prostitute, in no sacred bonds of marriage. When the woman whom he assumed to be a prostitute could not be located, he realized that he could fall into contempt, that is, for claiming to have had relations with a temple prostitute, when no such prostitute was known to be thereabouts.—Gen. 38:20-26.
As for Tamar, her course was not an adulterous one. Her twin sons were not considered to be the dishonorable sons of sin, sons of fornication. For, when Boaz of Bethlehem took the Moabitess Ruth in brother-in-law marriage, the elders of Bethlehem said to Boaz: “May your house become like the house of Perez, whom Tamar bore to Judah, from the offspring that Jehovah will give you out of this young woman.” (Ruth 4:11, 12) And so Perez is listed among the respectable ancestors of Jesus Christ. (Matt. 1:1-3; Luke 3:23-33) Perez’ mother, Tamar, was like Ruth in not going sexually after a young man.—Ruth 3:10.
As far as Judah was concerned, he thought he was having relations with a prostitute. In this he was not acting right, for it was God’s original purpose for a man to have relations with his wife and not for the earth to be filled with prostitutes. Still, Judah did not sin in the sense of transgressing a specific command of God’s law, for the Mosaic law was not given until much later.—Gen. 2:24; compare Leviticus 19:29.
The account about Judah and Tamar is not in the Bible to entertain. Rather, it forms an essential part of the historical narrative showing how the human line of descent leading to the promised Christ or Messiah, Jesus, was preserved.