Leviticus 5:4

Or if a soul swear, pronouncing with his lips to do evil, or to do good, whatsoever it be that a man shall pronounce with an oath, and it be hid from him; this is said of oaths as they are often made in trivial, foolish, unimportant matters, in heedlessness, recklessness, or passion, the person afterward forgetting or neglecting to keep the solemn promises and lightly disregarding the fact that such playing with sacred matters is sinful; when he knoweth of it, when it is brought to his attention and he does nothing to remove the sin, then he shall be guilty in one of these, in one of the three cases here enumerated.