Haircuts and Cutting Nails at Night

May I cut my hair and nails after chatzos (midday)?

Sifrei Kabbalah (Holy writings of Kabbalah) relate that the Arizal would refrain from having his hair cut after midday. Some are of the opinion that the same would apply to cutting nails. The question is: what was the reason for this custom?

If it was because we shouldn’t engage in any new melachah (work) once the zman (time) of Mincha has arrived—lest we be distracted from davening Mincha—then we can assume that there is no issue with cutting our hair after having davened Mincha. Nails, however, may be cut even before davening Mincha.

However, if the reason was that according to Kabbalah the forces of dinim (Heavenly judgment) begin gaining strength after midday, it would be cause to refrain from doing so throughout the entire afternoon, and in fact more so at night, when the dinim are even more severe. Although the influence of the forces of dinim is mentioned specifically only regarding haircuts, it can arguably be applied to nail cutting too. 

Common practice, though, is that we do take haircuts and cut our nails after midday—provided that we have davened Mincha—and at night as well. Likewise, If one has a fixed minyan for davening Mincha, one need not refrain from engaging in melacha prior to davening. #491

https://halacha2go.com?number=491

Practical Halacha: One minute a day. By Horav Yosef Yeshaya Braun, shlita, Mara D'asra and member of the Badatz of Crown Heights.