Weighty to take a vow to stay away from something that is permitted I take a vow to stay away from meat from saturated fats potato chips how I love potato chips or to take on something I think is right but is not required of me elevating the act to mitzvah status I vow to drive every single person who asks me to the airport any time they want.
Vows are a fence around separation [Avot 3:17] I take a vow in order to help separate from a problem distance or in our lingo abstinence you love those Little Debbie treats? Can’t eat just one? You’re hiding vodka around the house? Cruising the dark streets for white powder? Special problems require special strategies separation willing to go to any lengths with the vow in order to make a fence around the problem separate from it.
It’s serious this vow-taking Maimonides recommends we don’t do it at all let your yes be true and your no be true [Baba Metzia 49a] we are expected to do what we promise if we have to resort to vows something is wrong.
In conversation we say bli neder without a vow used in the sense of without a doubt if I have to take a vow I’m not good on my intention I need a vow to get something done? Do it.