Deuteronomy 21:12

Ver. 12. She shall shave her head, and pare her nails— Shaving the head was one of the external signs of mourning. See Leviticus 19:27; Leviticus 21:15. St. Jerome, and others, however, understand this shaving as a species of purification, and an abjuration of paganism. Paring the nails seems to have been also done in mourning. In the original it is, shall make her nails, which some understand of letting them grow; and this seems to us more suitable to a state of mourning; but the fashion of countries, as Calmet has well observed, must entirely determine; for we are told, that in some parts of America the women esteem it a beauty to have long nails; so that among them to pare the nails would be a sign of mourning; and this too is the case among the Chinese. Indeed, the custom of having long nails was common in Europe not above two ages ago.