Genesis 38:28 - Clarke's commentary and critical notes on the Bible

And it came to pass, when she travailed, that the one put out his hand: and the midwife took and bound upon his hand a scarlet thread, saying, This came out first. The midwife - bound upon his hand a scarlet thread - The binding of the scarlet thread about the wrist of the child whose arm appeared first in the birth, serves to show us how solicitously the privileges of the birthright were preserved. Had not this caution been taken by the midwife, Pharez would have had the right of primogeniture to the prejudice of his elder brother Zarah. And yet Pharez is usually reckoned in the genealogical tables before Zarah; and from him, not Zarah, does the line of our Lord proceed. See Matthew 1:3. Probably the two brothers, as being twins, were conjoined in the privileges belonging to the birthright.