6. Preparation & Attire:

Tevila:[1] It is customary for the Sandek to immerse in a Mikveh in the morning in honor of the Bris.

Aliya: The Sandek is considered a Chiyuv on the Shabbos before the Mila or Shabbos of the Mila and on the day of the Bris [if it falls on a  Monday or Thursday[2]].[3] Nevertheless, the custom today is not to be particular in this matter, and not to treat them as a Chiyuv for an Aliya, and rather they are given a different honor, such as Hagbah.[4] The Sandek is an even greater position than the Mohel, and hence receives precedence in getting an Aliyah to the Torah over the Mohel.[5]

Haircut:[6] It is customary for the Sandek to get a haircut in honor of the Bris.

Shabbos clothing:[7] It is customary for the Sandek wear Shabbos clothing for the Bris.

Tallis:[8] It is customary for the Sandek to wear a Tallis. [This was likewise the custom of the Rebbe Rayatz and Rebbe, who wore a Tallis upon being honored with Sandakaus.[9] According to Chabad custom, the Tallis is worn without a blessing if one had it in mind at the time of the wearing by Shacharis to also include the wearing of the Tallis by the Bris.[10]] On Tisha b’Av, if the Bris is taking place in the morning then a Tallis is not to be worn, although one is not to protest against one who does so.

Concentration:[11] At the time of the circumcision, the father of the child, Mohel, and Sandek are to prepare their minds and thoughts for the Mitzvah. In addition to the seriousness of the moment they should also be filled with joy that G-d has merited them to fulfill such a great Mitzvah which is similar to offering a sacrifice before G-d of which there is no greater level. If the Mohel has proper concentration, this will make a large effect above in heaven and this child will not hurriedly sin and the blood of the circumcision will be marked in the chambers of heaven near the throne of G-d.

[1] Maharil beginning of Mila; Birkeiy Yosef 265:18; Shevach Habris 17:7

[2] See Piskeiy Teshuvos 136:9 and 11

[3] M”A 282:18; Levush O.C. 282

[4] Shaareiy Efraim 2:1; Biur Halacha 136:1 “Beshabbos Veyom Tov”

[5] Rama Y.D. 265:11 “The power of the Sandek is even greater than that of the Mohel, and he hence is to receive precedence to the Torah”;

[6] Admur 493:4; Migdal Oz Nachal 9; Shevach Habris 17:7

Shevach Habris 16:7

[7] Michaber and Rama 551:1

[8] Pischei Teshuvah 265:13; Mateh Efraim 621:3; Koreis Habris 265:60; Sefer Matamim Erech Mila 59; Zocher Habris 17:16; Shevach Habris 17:7

[9] Shevach Habris ibid footnote 22

[10] See Chapter 9 Halacha 4 for the full details of the subject

[11] Levush 264:1; Migdal Oz Nachal 9, 11, and 12; Zocher Habris 17:15 and 18:16; Shevach Habris 17:9