Kommentar zu Bereschit 38:28

ויתן יד THE ONE PUT OUT HIS HAND — one stretched forth his hand outside, and after she had bound the scarlet thread upon his hand he drew it back.

על ידו שני לאמור, a scarlet thread on his hand, as though to say, etc. The midwife had a sudden flash of Holy Spirit and did something without being aware of its true significance. By tying Shani scarlet thread around his hand she indicated that the baby was Sheyni the one born second, though it had left the womb first. The Torah adds the word לאמור, "meaning to say" that this one emerged first. Although the midwife said so the truth was the reverse. The red thread was to prove יש אם למסורת, that there is a distinct significance to the spelling of a text as well as to the accepted way of reading a text.

ויהי בלדתה ויתן יד, one of them stuck his hand out of his mother’s womb, signaling that he wanted out. Seeing that he did not succeed, he withdrew his hand.

One extended his hand outside and after she tied... Rashi explains that it means “extended” because ויתן יד [would seem to] imply that the fetus intended to give her a hand. And Rashi says “one,” meaning that it was one of the two, because the verse does not state who put out his hand, nor does Scripture state המוציא or הנותן [as is usual when the subject is unidentified]. And Rashi adds, “After she tied the thread on it he withdrew it,” because כמשיב ידו [implies he put his hand back out, which] is understandable only if he had withdrawn it.

ותקח המילדת, she took hold of his hand before he could withdraw it.
ותקשור על ידו שני, as a sign who had been first.