“‘When a person sins in that he hears a public curse against one who fails to testify and he is a witness (he either saw or knew what had happened) and he does not make it known, then he will bear his punishment for iniquity.

or when he touches human uncleanness with regard to anything by which he can become unclean, even if he did not realize it, but he himself has later come to know it and is guilty;

“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

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 –

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.