The prohibition to think words of Torah or pray in a bathroom:[1]

It is Biblically forbidden to learn Torah or pray within a bathroom, just like it is forbidden for one to do so within [a four cubit radius] of excrement.[2] This Biblical prohibition applies even if the bathroom is clean of feces or urine.[3] It is forbidden to even think words of Torah without verbalizing them.[4]

May one think of the laws that pertain to a bathroom?[5] In a bathroom it is forbidden to even learn the laws that relate to a bathroom. [However, it is certainly permitted to think of a law pertaining to the bathroom in order to prevent one from sinning.[6]]

The severity of the prohibition:[7] If one transgressed the above and recited Shema [or learned Torah] within the forbidden area, on him it says[8] “Since you have disgraced the word of G-d… you shall be cut off..”.

A new bathroom:[9] If the bathroom is new and has yet to be used even one time[10], then there is no biblical prohibition involved in learning Torah or praying inside. Nonetheless, it is Rabbinically forbidden to verbalize words of Torah or prayer even in a new bathroom that has never yet been used.[11] [This applies throughout the entire parameter of the bathroom, within its walls, and applies even prior to the walls actually having been set up.[12] Nonetheless, most Poskim[13] conclude that it remains permitted to think words of Torah while there, until the bathroom is used even one time. Thus, it is permitted to listen to a Torah lesson while constructing a bathroom, so long as the bathroom has never yet been used even once before.[14]]

[1] Admur 83:1 [Kineged Beis Hakisei]; 82:1 [inside bathroom]; 85:1 regarding Muvaos Metunafos and inside bathroom; 74:1 regarding excrement; 76:9 regarding Ashpa; 87:1 regarding potty; Michaber 83:1; Brachos 26a

[2] The source: This is learned from the verse [Devarim 23:14-15] “Ki Hashem Elokecha Mis-haleich Bikerev Machanecha”. From this verse the Sages learned that in any area that Hashem walks with us, which is when one is in the midst of prayer and learning Torah, one’s encampment must be pure. [Admur 74:1; Rambam Tefila 4:8; Brachos 25b]

[3] Admur 82:1 and 83:1; Michaber ibid; Brachos ibid

The reason: As once the bathroom has been used it is considered repulsive and is not a holy encampment. [Admur ibid and ibid]

[4] Admur 83:1; 85:1; 84:1 regarding a bathhouse; Michaber 85:2; Rebbe Yochanon Brachos 24b; This is despite the fact that one is obligated to learn Torah day and night. [Admur 85:1]

Opinion of Yerushalmi: The Yerushalmi writes that it is permitted to think words of Torah in a bathroom. However, the Poskim explain that this refers to a case of Oness, such as a Talmid Chacham who cannot control his mind, and not to an initial allowance. [Beis Yosef 85 in name of Rav Manoach in name of Yerushalmi; See Kaf Hachaim 85:5

[5] Admur 85:1; Rama 85:2; Orchos Chaim in name of Ramban Shabbos 40b, brought in Beis Yosef 85; Ran, brought in Darkei Moshe 85; Levush; Soles Belula; This applies also according to the Michaber. [Kaf Hachaim 85:10]

[6] See Admur 85:4; So is also implied from the wording of Rama and Admur “to learn the laws of a bathroom” and not to think, [which was the case of the Michaber], as they are referring to actually learning for the sake of learning Torah.

[7] Admur 85:1; Brachos ibid

[8] Bamidbar 15:31

[9] Admur 83:2; 84:1; Michaber 83:2; Question of Ravina in Brachos 25a; Shabbos 10a-b; Rambam Kerias Shema 3:4; Rosh Brachos 3:57; Se Poskim in Kaf Hachaim 83:5; Piskeiy Teshuvos 83:3 

Background: It is Biblically forbidden for one to study Torah or pray or say a blessing inside of a bathroom or bathhouse, as that or requires that one’s camp [which refers to one’s area of prayer and Torah study] remain holy. However, if the bathroom or bathhouse is new and has yet to be used, then there is no biblical prohibition involved in doing so. Nonetheless, there is a rabbinical prohibition involved in verbalizing words of Torah or prayer even in a new bathroom that has never yet been used, being that since it has become designated for a purpose of filth it is therefore unbefitting to study Torah or pray to Hashem while there, even prior to it having become filthy for its first time. This applies throughout the entire parameter of the bathroom, within its walls, and applies even prior to the walls actually having been set up. Nonetheless, most Achronim conclude that it remains permitted to think words of Torah while there, until the bathroom is used even one time. However, by a new bathhouse, it remains even rabbinically permitted to verbalize words of Torah and prayer, until it is used for its first time, being that it’s filth is not as much as that of a bathroom.

[10] Admur 83:1; M”B 83:6; Biur Halacha 83:1; Vetzaruch Iyun if used one time only for urinating, and the implication is that it does not

[11] The reason: being that since it has become designated for a purpose of filth it is therefore unbefitting to study Torah or pray to Hashem while there, even prior to it having become filthy for its first time

[12] M”A 83:83:2; Machatzis Hashekel ibid; Levushei Serud ibid; P”M 83 A”A 2; M”B 83:9; Kaf Hachaim 83:5; Piskeiy Teshuvos 83:3 footnote 11

[13] Beir Heiytiv 83:2; Elya Raba 83; Ataz 83:3; P”M 83 M”Z 3; M”B 83:9; Kaf Hachaim 83:8; Piskeiy Teshuvos 83:3; However see Kesef Mishneh 3:4 who is stringent

[14] See regarding that hearing Torah from a tape recorder does not fulfill the obligation of Talmud Torah Bedibur: Admur Hilchos Talmud Torah 2:12; Machazik Bracha 47:4; Zekan Ahron 60; Halef Lecha Shlomo 35; See Sdei Chemed Asifas Dinim Mareches Rosh Hashanah 2:19; Halichos Shlomo 6:5