Leviticus 5:4, 17

Or if a person swears thoughtlessly with his lips to do evil or to do good, in whatever matter a man may speak thoughtlessly with an oath, and it is hidden from him, and then he comes to know it, he will be guilty in one of these.

“Now if a person sins and does any of the things which the LORD has commanded not to be done, though he was unaware, still he is guilty and shall bear his punishment.