Question: [Thursday, 29th Tamuz, 5782]
I did not yet cut my nails and just realized that tomorrow, Friday, is Rosh Chodesh? May I nevertheless cut them today even though it is Thursday which is a day that we generally avoid cutting nails? Is it better that I cut them Thursday, Friday, or not cut them at all?
If you are particular to cut your nails every Friday in honor of Shabbos, then you may do so also this Friday even though it is Rosh Chodesh, and should not cut them on Thursday. If you are not particular to cut them every Friday, then although you may not cut them on Friday, you may cut them on Thursday, if you forgot to cut them beforehand, in honor of Shabbos.
Explanation: The prohibition against cutting nails on Rosh Chodesh is due to danger, while the restriction against cutting nails on Thursday is a mere custom which is not universal. Accordingly, if one is faced with the choice of transgressing the Rosh Chodesh restriction versus transgressing the Thursday restriction, it is better to transgress the Thursday restriction. Now, regarding when Rosh Chodesh falls on erev Shabbos, it is disputed amongst the Poskim as to whether the nail restriction even applies, and the final ruling is the one who cuts his nails every Friday may do so even when Rosh Chodesh falls on Friday. Thus, certainly one who is particular to cut his nails every Friday is to do so this Friday as well even though it is Rosh Chodesh, and not precede doing so on Thursday. If, however, one is not always particular to cut his nails on Friday, then he may not cut them on Friday Rosh Chodesh. Accordingly, he is to cut them on another day during the week except Thursday. Now, if he forgot to cut them before Thursday, then he may cut them on Thursday in honor of Shabbos, as the restriction against cutting nails on Thursday only applies when one has the opportunity to cut them on Friday. If, however, the opportunity is not available on Friday, such as in our case due to the restriction of Rosh Chodesh, then he may cut them on Thursday, as it is being done for the sake of a mitzvah in honor of Shabbos, which overrides the issue of avoidance of cutting nails on Thursday. Aside for this being explicitly written in the Poskim, it is also what logic dictates, as the entire reason of avoidance of cutting nails on Thursday is because it’s not honorable to Shabbos to schedule the cutting of the nails in a way that they will begin growing back on Shabbos. However, it is much more disrespectful to Shabbos to enter into Shabbos with uncut nails. [Vetzaruch Iyun, as according to the opinion which avoids cutting nails on Thursday it is implied that it is permitted to cut the nails on Wednesday even though will begin growing back before Shabbos, and hence it is implied that it is better to enter Shabbos with a small amount of nails, then to cause the nails to begin growing back on Shabbos. Others however dispute this and rule that according to this opinion even before Thursday it is not to be done.]
Sources: See regarding the restriction of cutting nails on Thursday: Admur 260:2; Taz 260:1; M”A 260; Rashal; Mateh Moshe 411; Other opinions: The Aruch Hashulchan [260:6] argues against this custom. Likewise, he writes that all these cautions mentioned by nails are not required by the letter of the law, and one who is not particular in them, has not done any transgression; The reason: As the nails begin growing on the 3rd day after being cut and hence if they are cut on Thursday they will begin growing on Shabbos, thus some avoid cutting it on Thursday. [Admur ibid] Now, although there is no prohibition involved if the nails begin growing back on Shabbos, nevertheless it is not respectful that the nails which one ridded himself of in honor of Shabbos begins growing back on Shabbos. [Machatziz Hashekel 260:1; M”B 260:6 in name of Elya Raba] The above applies only to nails however a haircut may be given on Thursday being that hair begins to grow back that same day. [Kuntrus Achron 260:1] It is implied that this opinion is only particular regarding Thursday, however they allow one to cut the nails on Wednesday or another day of the week. See however Peri Megadim 260 M”Z 1 who brings the Elyah Raba who learns that this opinion holds that even before Thursday the nails are not to be cut, as then certainly one will have grown nails by Shabbos. This understanding however requires further analysis as if so then what is the dispute between this opinion and the previous opinion. Accordingly, they both hold the nails are to only be cut on Erev Shabbos. This is besides the fact that this is not the simple implication of Admur, and does not fit in with the explanation of the Machatzis Hashekel [260-brought in the footnotes to follow] behind the stringency. See regarding the restriction of cutting nails on Rosh Chodesh: Rav Yehuda Hachassid 49; Beir Heiytiv 260:2; Kneses Hagedola 260; omitted from Admur ibid and M”A ibid; The Ketzos Hashulchan 73 footnote 4 questions as to why no mention of this is made by the M”A or Admur in 260:1. See however Shaar Hakolel in Nesiv Hachaim 48:3; Shivim Temarim 57 who explain Admur omitted it because on Erev Shabbos it is Mitzvah to cut the nails even when it coincides with Rosh Chodesh. However on a non-Erev Shabbos Rosh Chodesh he would agree that one may not cut the nails. See next! See regarding the law if Rosh Chodesh falls on Friday: Lenient: Tehila Ledavid 260:1; Shaar Hakolel in Nesiv Hachaim 48:3; Shivim Temarim 57 as is the simple implication of the Kneses Hagedola ibid; Beir Heiytiv ibid; M”A and Admur ibid which omit the custom to avoid cutting nails when mentioning the custom to avoid cutting hair on Erev Shabbos Rosh Chodesh; opinions brought in footnotes on the Tzavah ibid; See Minchas Shabbos 72:66; Alef Hamagen 12; Maharam Brisk 2:99; Meishiv Halacha 2:4; Kitzur Hilchos Shabbos-Supplements; Stringent: M”B 260:7; Aruch Hashulchan 260:6; Kitzur SHU”A 72:14; Kaf Hachaim 260:12 allows only cutting the nails that stretch past the skin. See regarding that one may cut the nails on Thursday if he will not be able to cut them on Friday: Aruch Hashulchan 260:6; Piskeiy Teshuvos 260:5