When she was giving birth, one put out a hand, and the midwife tied a scarlet thread on his hand, saying "This one came out first." As he drew back his hand, behold, his brother came out, and she said, "How have you burst forth, making a breach for yourself!" And he named him Peretz.
The Ohr Hachaim explains that the midwife spoke with Ruach Hakodesh, and acted strangely without knowing why. She tied a scarlet thread, known as a שָנִי, which could also mean ‘the second’, around his hand. Although this baby emerged first, his complete birth was second. That is why the possuk says לֵאמֹר. All she did was say that this baby was first, but in reality, it was second.
When the second child emerged from his mother’s womb, the midwife called out, “How have you burst forth?!” The second child pushed the first one out of the way, and now the midwife’s prediction would not come true.
Additionally, the second child, having pushed his hand out first, would show that he was conceived first. If so, why was the second one allowed to be born first? This was the question of the midwife.
But now that we see that Peretz was the first to be conceived, we understand why his hand emerged first. And this is why he ends up being the ancestor of Dovid Hamelech and ultimately, Moshiach.
