Numbers 15 gives the provision for the atonement of unintentional sins.
If a person sinned unintentionally, breaking the Mosaic Law, the congregation could offer one bull from the herd for a burnt offering. They also were to provide a grain offering and its associated drink offering according to the Law, as this was pleasing to the Lord. For the sin, however, a single male goat would be offered unto the Lord as atonement for the unintentional sin.
This promise was given to the children of Israel, and was acceptable to all generations from that day onward. By doing this, not only were the sins of the one atoned, but the entire congregation as well. Even the strangers sojourning among them would be forgiven, because the whole population was responsible for the sins of the one.
This was a type of Christ. Through the blood of one Lamb, Jesus Christ, the sins of the world are forgiven. Through His sacrifice, our atonement has been provided, and all we need do is accept it by faith. His grace is sufficient for the atonement of our sins.
As Christians, we should ask ourselves: Do we ask Christ for forgiveness for our unintentional sins? Or do we think that because they were unintentional that we do not need repent? Are we led astray when evangelists tell us that "sin is unbelief," giving the perception that unintentional sin needs no atonement since we are believers? Do we accept the atonement Christ has provided for us?