2,669. Permitting an Oath for Purposes of a Mitzvah

Hilchos Shevuos 6:8

Both one who took an oath in private and one who took one in public may seek to have the oath permitted if he changes his mind; this is so even if one took an oath using the Tetragrammaton (God’s “four letter” name). However, if a person took an oath or a vow based on the knowledge and consent of numerous other people, it may only be permitted for the needs of a mitzvah.

Hilchos Shevuos 6:9

Pursuant to the previous halacha, let’s say that someone took an oath dependent on the knowledge and consent of other people not to benefit from a certain person. If the residents of that city need someone to teach Torah, or to perform circumcision or ritual slaughter, and they only find the one who took the oath, he may ask a Torah scholar or three lay people to permit his oath. The oath is permitted and he may perform these mitzvos for the city and be paid his salary from the residents from whom he had previously taken an oath not to benefit.