Parashas Acharei Mos · Passuk 18:10
Chabad.org — English translation + Rashi
Torah Temima points to Yevamos 97a.
English: One’s own granddaughter is forbidden; a woman’s granddaughter from another man is permitted under this verse — the later verse covers the case of marriage, this one the case of violation.
Granddaughter — own vs. wife’s
The prohibition of a granddaughter tracks the blood relationship of “your flesh,” not every granddaughter of a woman one has married.