פּירוש אויף בראשית 38:27

בעת לדתה AT THE TIME OF HER BEARING — But in the case of Rebecca Scripture says (25:24) “And when her days to give birth were fulfilled” — in the latter case the months of pregnancy were complete, here, however, they were short of the full term (Genesis Rabbah 85:13).

והנה תאומים בבטנה, “and here there were twins in her womb.” The midwife noticed this already before Tamar had commenced to give birth. This is why she had a means of identification ready to make sure the firstborn would be identified as such.

והנה תאומים בבטנה, she recognised shortly before giving birth that she was going to give birth to twins. This is the reason the midwife tied the red string to the baby first appearing out of her womb.

והנה תאומים AND BEHOLD TWINS — Here the word is written plene (with א and י whilst there (in the case of Rebecca) it is written defective (תומם without these letters) because one (viz., Esau) was wicked, but here both were righteous (Genesis Rabbah 85:13).