John Gill Commentary Leviticus 18:10

"The nakedness of thy son`s daughter, or of thy daughter`s daughter, even their nakedness thou shalt not uncover: for theirs is thine own nakedness." — Leviticus 18:10 (ASV)

The nakedness of your son's daughter, or of your daughter's daughter A man might not marry his granddaughter, whether a descendant of his son or of his daughter.

He might not marry any further off descending from him in a right line, not his great-granddaughter, and so on; and if he might not marry his granddaughter, much less his own daughter, as Jarchi observes, for the relation is still nearer; therefore that being prohibited, this in course must, though not mentioned: [even] their nakedness you shall not uncover ; neither debauch nor marry such an one:

for theirs [is] your own nakedness ; which sprung from his, being the descendants either of his son or daughter; the Targum of Jonathan is, ``for they are as your nakedness,'' his own flesh and blood.