- The Torah (Vayikra 19:27) says לא תקפו פאת ראשכם ולא תשחית את פאת זקנך meaning, don’t round the corner of one’s head and don’t destroy the corners of one’s beard.
- There are two negative commands to which the Torah warns, one of rounding the corners of the head and other of destroying the corners of one’s beard. 
- These are very serious Torah prohibitions and should not be ignored. 
- When cutting one’s hair or shaving in a permissible way one should intend to fulfill the Torah commands not to round the corners of the head or the beard. 
- The Kabbalists hold that it’s preferable not to cut one’s beard at all. 
Explanation of the prohibition
- The first is a command not to round the corners of one’s head which the Torah calls Peot HaRosh. The two areas that this prohibition includes is one on the left side of the head and on the right. 
- The prohibition is defined as cutting the hair that grows in front of one’s ear between one’s forehead and the area behind the ear.
- Women aren't obligated in the prohibition of Hakafat HaRosh. 
What is forbidden?
- It’s forbidden to cut the Peot HaRosh with a razor. 
- Some hold that it is forbidden to cut the Peot HaRosh with a scissor which cuts the hair close to the face.
- It’s forbidden to cut any hair in the area of Peot HaRosh. 
How long to leave the hairs
- It’s not considered cutting the Peot HaRosh if one leaves a half centimeter of hair and so it’s certainly permissible to cut the Peot HaRosh with a hair cutting machine that will leave the hairs with the length of half a centimeter (usually this is a number 2 on the hair cutting machine). 
Trimming, combing, plucking
- Trimming hair between the boundaries of Peot HaRosh is forbidden along the entire width. 
- It’s permissible to comb one’s hair in the area of Peot HaRosh since it’s not certain that one will remove a hair. 
- It’s forbidden to pluck a hair from that area and there’s an additional prohibition if one plucks a white hair from among black hairs. 
The upper boundary
- The upper boundary of Peot HaRosh is if one were to draw a straight line from the highest part of one’s ear (the middle of the curve) to the hairline on one’s forehead (from the edge of the hair on one’s forehead before the hair abruptly extends downward towards the ear). This upper boundary is different for every person. 
- Because of lack of knowledge, some cut the hair around the ear on the front side until the middle of the ear (the highest point of the ear) which is actually forbidden. However, from the behind the ear (from the middle of the ear) it’s permissible to cut the hair. 
- Because of lack of knowledge, some leave long Payis but still violate the prohibition by cutting the hair below the hairline (leaving less than a half centimeter) and only leave payis starting from next to the ear. 
- If a person has hair that juts out from the hairline on one’s forehead, this is not considered in determining the hairline of the forehead. 
- Someone who went bald should consider his hairline from the area where hair used to grow. 
The lower boundary
- The lower boundary of the Peot HaRosh according to the letter of the law is where the upper jaw bone separates from the skull bone, which can be felt when one opens one’s mouth.  However, some say one should leave it until where the ear separates from the face and some say that one should leave until the bottom of the ear. 
- Those who are strict not to cut until the bottom of the ear where it separates from the face or from the lowest point on the ear should not cut anywhere along the width of that boundary. 
- Rambam (Intro to Avoda Zara counts Hakafat HaRosh and Giluach HaZaken as two separate negative commands.
- Sh”t Tashbetz 3:127 s.v. Lo Nichad writes that those who constantly violate this sin consider it as if the prohibition wasn’t written explicitly in the Torah and those people are considered like violating all of the Torah and their ritual slaughter isn’t acceptable!!
- Pela Yoetz (Paragrah “Geluach”) writes that not violating the negative command is like fulfilling a positive command and one should intend to fulfill it actively.
- Birkei Yosef 181:10 in name of the Arizal. See also the Meor Yisrael who quotes the Bava Sali who says that have a beard and not cutting it brings forgiveness for one’s sins!
- Mishna Macot 20a and Rashi there s.v. Chayav
- Gemara Macot 20b; see Rashi there("hamashve"), and Kiddushin 35b for Rashi's comment on "hakafat harosh".
- Kiddushin 29a, S”A Y”D 181:6
- See Tur and S”A 181:1.
- Shulchan Aruch Y”D 181:3. According to the Rambam it’s only forbidden to cut the Peot HaRosh with a razor and it’s permissible to cut it with a scissor close to the face, however, the Rosh forbids cutting the Peot HaRosh even with a scissor close to the face.
- Even though the Rambam (Avoda Zara 12:6) writes that it’s only forbidden if one leaves less than 40 hairs, the Smag (quoted by Bet Yosef Y”D 181) holds that it’s forbidden to cut even 2 hairs. Therefore, S”A Y”D 181:9 rules that one may not cut any hairs of the Peot HaRosh.
- Peot Zekenecha (pg 19, 30) in name of Rav Elyashiv based on the measure given in the Gemara Niddah 52b and Rambam Nezirut 5:11 that leaving hair which can be bent over and reach the root is not considered cutting the hair. LeShechno Tidroshu (vol 1 pg 300) writes similarly.
- S”A Y”D 181:9, Peot Zekenecha (pg 41)
- Peot Zekenecha (pg 42)
- Kaf HaChaim 27:13, Peot Zekenecha (pg 56)
- S”A 181:9, Peot Zekenecha (pg 22, 26, 28)
- Peot Zekenecha (pg 44, 47) in name of the Chazon Ish
- Beiur Halacha 251:2
- Peot Zekenecha (pg 23) in name of Rav Chaim Kanievsky and Rav Nassim Karlitz
- Peot Zekenecha (pg 22) in name of Rav Chaim Kanievsky and Rav Nassim Karlitz
- Rashi Macot 20a s.v. Chayav writes that the Peot HaRosh extend until where the jaw bone separates from the skull bone. Tur 181:9 rules like Rashi. Leshechno Tidroshu pg 300 and Peot Zekenacha in name of Rav Nassim Karlitz write that the strict law is the separation of the bones.
- S”A 181:9 first writes like the language of Rashi and then continues that Peot HaRosh extends to the bottom of the ear. Peot Zekenecha (pg 48) quotes two explanations of the S”A; some say that it’s from where the ear separates from the face and some say it’s until the lowest part of the ear.
- Peot Zekenecha (pg 54)