The whole story in Genesis 38 is one big, confusing, sinful mess. It doesn’t matter whether you’re talking about Judah, Tamar, Onan, Er, or basically anyone else, the entirety of the chapter is filled with immorality.
It’s interesting then, that in the middle of all of this sin, Judah, who slept with (what he thought was) a prostitute earlier in the chapter, decrees someone else as “righteous.”
It’s possibly even more shocking that that person he calls righteous is someone who impersonated a prostitute to get pregnant by her father-in-law.
It’s like some backwards version of the pot calling the kettle black.
But in this situation, I would tend to agree with Judah. Of the two people — Tamar and Judah — Tamar was the more upright one. This despite knowingly committing adultery.
There are several clues to what happened along the way. For starters, Judah tells Tamar to wait and “remain a widow” in her father’s house while Judah’s youngest son Shelah grew up. What he didn’t tell Tamar was that he was scared that Shelah would die like his brothers, thus leaving him without a genealogical line (Genesis 38:11).
Ironically, this fear almost became a reality because of his inaction.
By Genesis 38:14, Shelah is a grown man and Tamar is still not given to him as a wife to raise up offspring. Seeing the hours slip away, she takes matters into her own hands by impersonating a prostitute and becoming pregnant with Judah’s child. Through this, the line of Judah continues.
Was it deceitful? Yes. Was it sexually immoral? Yes, especially considering Tamar was still considered Judah’s daughter-in-law (Genesis 38:24-25).
But at the very least, it was a prudent action on Tamar’s part to take matters into her own hands to save Judah’s genealogy. Judah’s statement also signifies that he recognizes his own sinfulness in the matter and what has happened as a direct result of his actions.