halacha - Rules for Cutting Nails

My question about nail-cutting is whether each of the following is halacha, minhag, or old-wives' tales.

1. Not cutting both fingernails and toenails on the same day.


2. Not cutting nails at night (is this after shkiah, tzeis?).


3. Not cutting the digits in order.


4. Not cutting nails on Thursday (so they won't start growing on Shabbos).

I'm pretty sure #3 and #4 are halacha (Shulchan Aruch), but I wonder about the other two. Are there any other rules I'm forgetting?

Answer

The Shulchan Aruch in O.C. 260:1 says it is a mitzvah to trim ones nails on erev Shabbos. The Rema (ibid) adds that one should not trim them consecutively. Although the Taz 260:2 (based on the תשב"ץ and the Ariza"l) says one need not be concerned about this, the Magen Avraham 260:1 says that nevertheless one should be careful. This is echoed by the Shulchan Aruch HaRav 260:3, and Mishneh Berurah 260:8.

The Mishneh Berurah (260:6) mentions that it is the practice not to trim one's nails on Thursday. It is also mentioned there that there are authorities who say one should not trim one's finger nails on the same day as they trim their toenails.

The Mishneh Berurah also cites the Gemara (See Niddah 17a, Moed Katan 18a) which says one who burns their nail trimmings is a Chasid (pious person), one who buries them is a Tzadik (righteous person), and one who trows them out (haphazardly) is a Rasha (wicked person). It proceeds to explain that it is sufficient if one sweeps from their original location there is no need for concern, but cites the Elya Rabba that only when they have been removed from the original room is it considered a change of location (ibid 5).

I have not seen, to my recollection, any mention that one should refrain from trimming one's nails at night, but have seen one should not do so on Rosh Chodesh (Be'er Heitev 260:2 citing the Will of R. Yehuda haChasid) and that one should only trim one's fingernails on erev Shabbos or erev Yom Tov (Be'er Heitev ad loc).

There is a practice to trim ones fingernails and toenails on Erev Shavuos, since this is the practice of women prior to ritual immersion and on Shavuos Am Yisrael is, as it were, the kallah (bride) of Hashem.