"You are Israel's teacher, and do you not understand these things?"
Leviticus 5:17-19
“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. It is a guilt offering; he was surely guilty before the Lord.”
(This is probably just another of those Jewish traditions...)
Yes, more or less, it is. The Old Testament Law was absent grace and was given the Jews in order to give them simple rules easy to follow. Christianity arrives to a deeper understanding of sin as willful defiance of God, not an ignorant mistake. Note, also that the Hebrew Law is very lenient in this case.