Rashi (Bereishis 38:27) notes the difference between the term תאומים used for Tamar’s pregnancy and תאמים used for Rivka’s. In Tamar’s case, both children were righteous, whereas Rivka bore Yaakov, a tzaddik, and Esav, a rasha. The Torah’s need to highlight this distinction suggests that there is a fundamental similarity between these two pregnancies. What is that comparison?
Regarding Zarach’s birth, Rashi comments that the phrase “ארבע ידות” appears, alluding to the four acts of treachery committed by Achan, who descended from Zarach. Others explain that it refers to the four items Achan took: a Shinar garment, two silver pieces totaling 200 shekels, and one golden tongue. Why is Achan’s sin hinted at here?
The Ramban, citing the Bahir, explains that Peretz and Zarach correspond to the sun and the moon. Zarach, whose name suggests “shining,” represents the sun—constant and unwavering. Peretz, whose name implies “breaking through,” parallels the moon, which waxes and wanes. What does this symbolism mean? Zarach embodies the tzaddik, whose light shines steadily and whose path is straightforward. Peretz represents the baal teshuva, whose spiritual journey includes ups and downs but ultimately reaches greater heights. This is why Mashiach descends from Peretz for the transformative power of teshuva surpasses the static righteousness of the tzaddik (see Likkutei Sichos vol. 30).
The Torah distinguishes between Yaakov and Esav, and between Peretz and Zarach, because the potential dynamic was similar. Yaakov parallels Zarach—the tzaddik—while Esav could have mirrored Peretz, becoming a baal teshuva. Instead, Esav succumbed to his lows and never rose above them.
The Maharal expands on the Ramban’s sun-moon analogy, noting that Achan’s four transgressions correspond to the four acts of betrayal against the four designated cherem items, reflecting the power of the sun created on the fourth day. Unlike the moon, which fluctuates, the sun is fixed and limited. Achan’s sin lay in trying to emulate Peretz—seeking expansion beyond his boundaries and taking what was not his. This overreach led to his downfall.