Reuven is walking with his friend or his rabbi in the street, and Reuven needs urgently to use the bathroom. If the friend or rabbi is talking to him in learning, is it permitted to listen and even to respond to what is being said? If one can avoid answering back (e.g., to say that he doesn’t know what the answer is or that he needs to think about it), should he do so, even if he really does know the answer – in order to avoid saying words of Torah while needing the bathroom?
It depends on how badly he needs the bathroom. If he didn’t need to use the bathroom before they started talking, he is allowed to continue talking even if now he can’t wait 72 minutes to use the bathroom. He is allowed to listen and to respond since he started when he was allowed to he is allowed to finish what he is learning.
He may also start learning if he feels that he will be able to wait 72 minutes, however if he will not be able to wait so long he shouldn’t start.
However if he now has a strong urge, (and he has to “hold himself back”) since the needs had reached ba’al tishaktzu, he has to stop talking in learning, (with the exception if he is speaking in public, he doesn’t have to embarrass himself, and he may continue). However he is permitted to listen to learning even if he has already reached ba’al tishaktzu.
B”H 92 D”H Koreh Kidarcoy, D”H Aval Blav Hachi, M”B ibid 7,10,. Listening to torah and baal tshaktzu- Hagaos Mimonis Tefiloh 4-8,Merok Chaim, Shevet Hakehosi 6- 80.