Genesis 38:26-30

And Judah recognized them, and said, “She is more righteous than I, since I did not give her to my son Shelah.” And he did not have relations with her again.

It came about at the time she was giving birth, that behold, there were twins in her womb.

Moreover, it took place while she was giving birth, that one baby put out a hand, and the midwife took and tied a scarlet thread on his hand, saying, “This one came out first.”

But it came about as he drew back his hand that behold, his brother came out. Then she said, “What a breach you have made for yourself!” So he was named Perez.

Afterward his brother came out who had the scarlet thread on his hand; and he was named Zerah.