Leviticus 5:19 net — It is a guilt offering; he was surely guilty before the LORD.”

And whatever holy thing he violated he must restore and must add one fifth to it and give it to the priest. So the priest will make atonement on his behalf with the guilt offering ram and he will be forgiven.”

Unknown trespass“If a person sins and violates any of the LORD’s commandments which must not be violated(although he did not know it at the time, but later realizes he is guilty), then he will bear his punishment for iniquity

and must bring a flawless ram from the flock, convertible into silver shekels, for a guilt offering to the priest. So the priest will make atonement on his behalf for his error which he committed(although he himself had not known it) and he will be forgiven.