Leviticus 5:4

5:4 or when a person swears an oath, speaking thoughtlessly with his lips, whether to do evil or to do good, with regard to anything which the individual might speak thoughtlessly in an oath, even if he did not realize it, but he himself has later come to know it and is guilty with regard to one of these oaths –

Leviticus 10:6

10:6 Then Moses said to Aaron and to Eleazar and Ithamar his other two sons, “Do not dishevel the hair of your heads and do not tear your garments, so that you do not die and so that wrath does not come on the whole congregation. Your brothers, all the house of Israel, are to mourn the burning which the Lord has caused,