May one wrap the Tefillin over his wristwatch or must he remove it?

A. Background of the laws of Chatzitza by Tefillin:[1]

The dispute: Some Poskim[2] rule that one is required to make sure that there are no intervening substances between the Tefillin and one’s skin [as if there is an intervening substance the wearing of the Tefillin is invalid].[3] This applies to both the Tefillin Shel Yad and likewise to the Tefillin Shel Rosh, that one needs to be aware that there is no intervening substance between the Tefillin and his hair. [This applies only to those areas of the Tefillin brought in Halacha B!] It is due to this reason that some are accustomed to wash the area of hair where the Tefillin rests. Other Poskim[4], however, rule that there is no need at all to beware that there not being intervening substance between the Tefillin and one’s skin or hair [and the wearing of the Tefillin is valid even in such a case].

The final ruling:[5] The final Halachic ruling is not like the latter opinion [and hence one must beware that there are no intervening substances between the Tefillin and his skin or hair]. Nonetheless, in certain cases to be mentioned, one may rely on the lenient opinion and wear the Tefillin on an intervening substance. 

The areas that may not contain a Chatzitza?[6] One is required to make sure that there are no intervening substances between the Bayis of the Shel Yad and where it rests on the skin of the bicep, nor between the Bayis of the Shel Rosh and the hair that it rests on by the head.[7] Likewise, there may not be any intervening substances under the straps, throughout the entire area where the straps rest on the head, as well by the area of the skin where the tying [of the Shel Yad] takes place, which is the area of the bicep where the first strap of the Shel Yad is wrapped.[8] [It is implied there may not have any intervening substances of any amount under these areas, and if one does then it is invalid.[9] However, by the other areas that the strap is wrapped, such as under the area of the strap that is wrapped around the forearm and hand, or even the additional straps wrapped around the bicep, there is no disqualification if there are intervening substances present.[10] Nonetheless, some Poskim[11] rule that one is not to have an intervening substance under any of the first few straps that are wrapped around the bicep and arm, and hence those accustomed to make a Shin by the bicep are not to have any Chatzitza’s under these straps. Furthermore, some Poskim[12] rule that initially it is proper to be careful to not have any Chatzitza’s even under other areas of the straps, with exception to the straps of the head Tefillin which dangle by the chest, that they may dangle over the clothing. Likewise, one is to initially avoid having a Chatzitza by the area of the fingers that the straps around.[13]]  

B. The law by a wristwatch:[14]

From the letter of the law, it is permitted to have a Chatzitza under the areas of the straps that are on the arm, and hence it is permitted to wrap the straps over a watch that one is wearing. [Accordingly, there is no need by Mivtzaim to make sure that the person removes his watch.] Nonetheless, it is initially proper to be stringent to remove the watch in order not to have a Chatzitza even under the straps.

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[1] Admur 27:7

[2] 1^st opinion in Admur ibid; Siddur Admur [letter 4 in Raskin]; Michaber 27:4; Tur 27; Rosh Tefillin 18

[3] The reason: As the verse [Shemos 13:9] states “On your hand” which implies that it must rest on the actual [skin of the] hand without any intervening substance in between. [Admur ibid; Taz 27:3; Shut Harosh 3:4]

[4] 2nd opinion in Admur ibid; Rashba Megillah 24b, brought in Ran Megillah ibid; Teshuvos Harshba Orchos Chaim Hilchos Tefillin 18; See also Shut Rashba 3:282; Teshuvos Hameyuchasos Leramban 233

[5] Admur ibid; Siddur Admur [letter 4 in Raskin] “One is to be careful not to have any intervening substance between the Tefillin and his skin.”; Michaber ibid

[6] Admur 27:7

[7] Admur ibid; Michaber 27:4

[8] Admur ibid; Taz 27:4 in name of Levush 27:4 “Rabbi Yaffe writes that the custom is to be stringent regarding the straps that perform the tying by the head and hand Tefillin, and this is a proper approach”; Rashba 827, brought in Taz ibid and M”A 27:5, that the custom is to be stringent even under the strap; Olas Tamid 27:4; Elya Raba 27:4; Yad Aaron 27; Shalmei Tzibur p. 38; Siddur Beis Oveid Hanachas Tefillin 17; Shesilei Zeisim 27:11; M”B 27:16 in name of Olas Tamid, Elya Raba, Gra; Kaf Hachaim 27:20; Ketzos Hashulchan 8 footnote 22; See Piskeiy Teshuvos 27:9

Other opinions: Some Poskim rule that the issue of an intervening substance is only relevant to under the actual Bayis, however under the straps there’s no need to worry of an intervening substance. [Rama 27:4; Initial suggestion in Rashba 827, brought in Rama 27:4; and M”A 27:5] This implies that there is no disqualification of an intervening substance under any area of the straps, even by the first strap of the bicep and the straps that rests on the head. [Taz 27:4] However, in truth, the Rashba ibid concludes that one is to follow the custom which is to be stringent, and it is hence puzzling that the Rama took a lenient approach. [Taz ibid; M”A 27:5] See M”A 27:5 that the intent of the ruling of the Rashba is that when may not wrap the straps over a garment, although a slight amount of interval is valid. Some Poskim conclude that in a time of need, such as one who has a bandage on his head/bicep, we allow him to wear the Tefillin with a blessing even though the straps are sitting on the bandage so long as there are no bandages under the Bayis itself. [M”B 27:16 in implication of M”A ibid and Chayeh Adam]

[9] Implication of Admur and Taz ibid; See Piskeiy Teshuvos 27 footnote 87

Other opinions: Some Poskim rule that a small Chatzitza under the straps is valid. [M”A 27:5]

[10] Admur 27:7; Taz 27:4; Rama 27:4 “However under the straps there’s no need to worry of an intervening substance”; Derech Hachaim; Shenos Chaim; Shut Stam 54; Piskeiy Teshuvos ibid footnote 64, 67; See Yabia Omer 2:2; Yechaveh Daas 3:2

Other opinions: The M”A 27:5 rules that one may not wrap the straps over a garment, although a slight amount of interval is valid. It is unclear if his intent is then we should not have an intervening substance even under the straps throughout the arm.

[11] Os Chaim Veshalom 27:7

[12] Peri Megadim 27 M”Z 4; Shesilei Zeisim 27:11; Yad Eliyahu 3; Kaf Hachaim 27:20; Doveiv Meisharim 2:37; Cheshev Haeifod 1:21; Teshuvos Vehanhagos 2:26; Piskeiy Teshuvos 27:9

[13] Chasam Sofer Y.D. 192

[14] Doveiv Meisharim 2:37; Cheshev Haeifod 1:21; Teshuvos Vehanhagos 2:26; Piskeiy Teshuvos 27:9