Shabua tob, I’d like to know if there is a mekor for what people say that one should not cut his fingernails at night. Thanks
See Shu”t Yechave Daat from Rav Ovadia Yosef 4:20 who quotes from Rav Chaim Palagi that according to the kabala one should not cut hair or nails by night. Rav Ovadia disputes this, and claims that there is no problem according to halacha or kabbala to do so at night.
See Yerushakmi Tannit 4:9 who implies the custom was to cut hair at night.