Leviticus 5:3, 6, 17

or if they touch human uncleanness (anything that would make them unclean) even though they are unaware of it, but then they learn of it and realize their guilt

As a penalty for the sin they have committed, they must bring to the LORD a female lamb or goat from the flock as a sin offering; and the priest shall make atonement for them for their sin.

“If anyone sins and does what is forbidden in any of the LORD’s commands, even though they do not know it, they are guilty and will be held responsible.