Thomas Jefferson once said that "...ignorance of the law is no excuse." This concept is a Biblical one, as found in the Old Testament law in passages like Leviticus 5:17-19. Just because "you didn't know" doesn't mean that you are not guilty.
This idea is foundational to understanding our sin nature as well as the mercy and grace of God. I am struck in reading these passages in Leviticus, because God mercifully made a way for forgiveness, even in the midst of our ignorance. "While we were yet sinners, Christ died for us." (Romans 5:8). Even before we recognized our need for a Saviour, Christ had it covered - with His blood.
As our society loses its sense of personal responsibility, it seems that people get offended more and more at the suggestion that they are sinners in need of a Saviour. If a bridge were out on a road on which a person was speedily driving, they will be just as dead if they go over the edge of that cliff in ignorance as they would if they saw a sign that said, "Bridge Out Ahead," and proceeded anyway. The fact is, there are consequences for sin, whether or not we want to hear about it; and there is mercy and forgiveness waiting.
As born-again believers, we have a responsibility to warn the lost of their ignorance. It may be a thankless job at times, but one that is eternally important. May we purpose to be ever faithful to our efforts in winning souls and delivering sinners from the ignorance of entering eternity without the mercy and grace of God applied to their account. Psalm 126:6 says, "He that goeth forth and weepeth, bearing precious seed, shall doubtless come again with rejoicing, bringing his sheaves with him."
Leviticus 5:17-19 "And if a soul sin, and commit any of these things which are forbidden to be done by the commandments of the LORD; though he wist it not, yet is he guilty, and shall bear his iniquity. (18) And he shall bring a ram without blemish out of the flock, with thy estimation, for a trespass offering, unto the priest: and the priest shall make an atonement for him concerning his ignorance wherein he erred and wist it not, and it shall be forgiven him. (19) It is a trespass offering: he hath certainly trespassed against the LORD."