“When her days to be delivered were fulfilled, behold, there were twins in her womb.” Gen. 25:24
Rashi notes that in the original text, the word for “twins” is missing a letter. Compare to Genesis 38:27 when the same is said of Tamar’s twins, but the full spelling is present. Though we may merely consider this a scribal error, Rashi believes there is a significance due to how the story of Jacob and Esau ultimately plays out; that perhaps Esau is deficient in some way, morally speaking, as opposed to Tamar’s sons, Perez and Zerah.
We also see an interesting pattern with the birth order between these two stories; with Jacob and Esau we see the struggle in the womb, and though Esau is born first and gets the birthright, it is tricked out of his hands by his brother. With Perez and Zerah, Zerah’s hand came out first, and the midwife tied a scarlet thread to him so they would know who was who, but ultimately Perez was fully born first. It is as if there is a shifting of order of things. Perhaps this has something to do with Christ’s teaching that “the first shall be last and the last shall be first.”
As for the missing letter, consider Ephron, the son of Zohar, who sold the Cave of Machpelah to Abraham for burial at a highly inflated price; Ephron’s name changes in the original Hebrew after that transaction. Contrast this with Abram and Sara, who were renamed by God, having an “H” added to both of their names: Abraham and Sarah.
The scriptures speak of a Book of Life in several places in both Testaments; Of names being blotted out of the Book, and names being added to the Book. Perhaps this is done one letter at a time.