Should one miss zman tefilah if he needs to relieve himself?

It is forbidden to daven or learn Torah if one needs to relieve himself. Even if one has to forfeit tefilah b’tzibur, he may not daven in this compromised state. If one did daven, his tefilah is not valid. If a person knows that he can control his urge to relieve himself for at least seventy-two minutes, his tefilah is valid b’dieved. Even if he enters the bathroom immediately after completing Shemoneh Esrei, he is yotzei since he technically could have waited. One who is concerned that he will miss zman tefilah may daven l’chatchilah if he can control himself for seventy-two minutes.

סימן צ"ב ס"א ס"ק ג'-ו' ביאורים ומוספים דרשו 3

Is a lecturer obligated to interrupt his shiur if he must relieve himself?

Aside from the prohibition against davening or learning when one has to relieve himself, there is a general prohibition against holding oneself back from using the restroom.  This issur is known as bal tishaktzu. To transgress this prohibition, one must have a strong need to relieve himself. This issur is only mid’rabonon. Therefore, if one is giving a lecture and it will be embarrassing for him to interrupt it and tend to his needs, he may finish the class. The discomfort which he would suffer otherwise is an issue of kavod habrios, which overrides a rabbinic prohibition. Kavod habrios is relative to the sensitivities of the individual. If one is not uncomfortable interrupting his class, he is obligated to do so.

ס"ק ז וי' ביאורים ומוספים דרשו 10

May one interrupt between geulah and tefilah to use the restroom?

If a person did not have the need to relieve himself when he began Shemoneh Esrei but the urge to do so arose in the middle of davening, the Shulchon Aruch holds that he is not allowed to interrupt his Shemoneh Esrei. Once he finishes, he must immediately tend to his needs; he should not wait for Kedusha. If the need arises while he is in the middle of Kriyas Shema, he may choose to complete Shema but it is forbidden to continue on to Shemoneh Esrei. It is best to use the restroom between Shema and Emes V’yatziv. If he did not do so, he should go in the middle of the brocha but not at the end of the brocha, so as not to interrupt between geulah and tefilah. Nevertheless, if he has an urge right before Shemoneh Esrei he must relieve himself, even if he will have to interrupt between geulah and tefilah.

ס"ב ס"ק ח-ט ביאורים ומוספים דרשו 14

• Chazal teach that a person must adjust his clothing before davening Shemoneh Esrei. These preparations include tightening a belt or gartel around his waist. Even if a person already has a belt which separates between his heart and ervah, he must add another one to fulfill this halacha.

• The poskim discuss whether it is permissible to greet a bareheaded person with the word Shalom (a name of Hashem), as there is a concern that he may return the same greeting. Some are lenient, since the bareheaded person does not intend to use the word in reference to Hashem.

• On Purim, one may daven while wearing a costume as long as he is properly covered and he is not engaging in levity during davening.

• Must a person stop learning if he suddenly needs to relieve himself?

• Should one stop in the middle of Shemoneh Esrei to use the bathroom?

• Under what circumstances would one have to repeat Shemoneh Esrei?