Sefer Ha’mitzvos Ha’Katzar (The concise book of mitzvos)
By the Chofetz Chaim
This book lists the Torah mitzvos that can be observed today
First Section – the Positive Commandments
40. It is a positive commandment to judge cases of nullifying vows and oaths
As it states in Bamidbar (Numbers) 30:3, "When a man that takes a vow to G-d." This means that when a person makes a vow and later feels sorry on what he did, he shall go to a expert wise man or, three regular men if there is no expert there, and say 'I swore or vowed such and such a thing, and now I regret it. If I knew that I would suffer so much from this thing or such a thing would happen to me, I would not have made the oath or vow.' The wise man or the three regular men ask, 'Have you already been regretting it?' And the man says back, 'yes'. Then, the wise man or three regular men say to him, 'It is allowable to you' or 'it is forgiven to you' or 'it is permissible to you'.
This applies in all places and at all times.