The Laws Governing Vows and Oaths
1. One should not make vows [nedorim] frequently. Anyone who makes a vow is
considered as if he built an altar in the high places outside Jerusalem at
a time when the construction of such alters is forbidden. Should he fulfill
the vow, it is considered as if he sacrificed an offering upon [the alter
he built. This is equivalent to the violation of] the prohibition against
sacrificing outside the Temple premises (Nedorim 22a). [Even though he was
obligated to fulfill his vow,] it would have been preferable to seek to
have the vow annulled [as explained in Law 8].
The above applies to vows of a general nature. However, it is a mitzvoh to
fulfill vows made to consecrate an object to the Temple, as [Psalms 116:14]
states: "My vows to G-d, I will fulfill" One should seek to absolve them
only in times of emergency (Vayikro Rabboh 37:4).
2. Similarly, a person should avoid taking an oath [sh'vu'oh]. However, if
he erred and did make an oath concerning a particular matter, he should not
try to absolve it. Rather, he should maintain his oath even though it
causes him difficulty [as implied by Psalms 15:4]: "One who swears to his
own distress and does not alter it..." and the following verse continues:
"Those who do these things shall never stumble." One should seek to absolve
an oath only in times of emergency.
3. A person should take care not to make any vows. It is even preferable
not to vow to give charity. Rather, if one possesses something to charity,
he should give it immediately; if one does not possess the means at
present, he should wait until he does, and then give without taking a vow.
If pledges are being made to charity and an individual also desires to make
a pledge, he should specify that the pledge is being made without
obligating himself with a vow [Bli Neder]. Similarly, in the Yizkor
prayers, when one pledges to give money to charity, one should state that
the pledge is being made without obligating oneself with a vow. In a time
of emergency, one is permitted to vow.