Nedarim 9 - Careless people
If one says, "Like the vows of the careless people" - with this statement he has effected a vow, and must now abide by its conditions. Careless people were swift to make vows or to swear, in anger or just to convince, and this man, while disapproving of them, still followed their example. This is an incomplete vow, which nevertheless takes effect.
But this vow is too incomplete, he in fact said nothing binding! - Really, he then added, "on me." But what is exactly is his vow? What limitation did he put upon himself! - A Nazir was passing in front of him, or he added "Of this I will not eat."
If, after all, he has specified so much, what new information has the teacher told us? Of course the vow should work! - Well, although he did not enunciate "I hereby take a vow," his declaration of "Like the vows of the careless" still took effect.
If he said "Like the vows of the righteous," it is as if he has not said anything, because righteous don't make vows. However, if he said, "Like their free-will offerings," he should follow the good example of the righteous and do what he promised.
King Solomon said, " Better not vow at all than vow and not pay ." What about one who vows and does pay? Some say that it is still better not to vow at all, but some - that vowing and the fulfilling the vow is better than anything.
Rienzi Vowing to Obtain Justice by William Holman Hunt