The seven days, while their feast lasted, i.e. on the residue of the seven days, to wit, after the third day. It is a familiar synecdoche. Or, on the seventh of the days on which the feast was; and then the following clause, on the seventh day, is only the noun repeated for the pronoun, on that day; as is most frequent, as 1 Kings 8:1, Solomon assembled unto Solomon, i.e. unto himself.
Related Commentaries of Judges 14:17
Judges 14:17
17 And she wept before him the sevend days, while their feast lasted: and it came to pass on the seventh day, that he told her, because she lay sore upon him: and she told the riddle to the children of her people.