Osek b'mitzvah patur min hamitzvah
In Judaism, the concept of Osek B'Mitzvah Patur Min Hamitzvah sometimes exempts one from performing a religious obligation while one is engrossed in another religious obligation.Extensions of the rule
The Talmud makes use of a similar concept in reference to those who are not yet actively engaged in a mitzvah but also to those who are busy preparing to perform a mitzvah, with the comment that שלוחי מצוה are similarly exempt from performing other religious obligations, such as sitting in a sukkah.
The Pnei Yehoshua comments that such exemptions are valid only for positive commandments, stating that one thoroughly engaged in a positive precept would certainly not enable one to violate negative precepts.
