Sins unintentionally: the sin they committed becomes known

 Leviticus 4-5

If the anointed priest sins: The Sin Offering: bringing guilt on the people, he must bring to the Lord a young bull without defect as a sin offering for the sin he has committed. 4 He is to present the bull at the entrance to the tent of meeting before the Lord. He is to lay his hand on its head and slaughter it there before the Lord.

If the whole Israelite community sins unintentionally:  the sin they committed becomes known, the assembly must bring a young bull as a sin offering and present it before the tent of meeting. The elders of the community are to lay their hands on the bull’s head before the Lord, and the bull shall be slaughtered before the Lord.

When a leader sins unintentionally and does what is forbidden in any of the commands of the Lord his God, when he realizes his guilt and the sin he has committed becomes known, he must bring as his offering a male goat without defect. 

If any member of the community sins unintentionally and does what is forbidden in any of the Lord’s commands, when they must realize their guilt. They must bring as their offering for the sin they committed a female goat without defect. They are to lay their hand on the head of the sin offering and slaughter it at the place of the burnt offering.

If someone brings a lamb as their sin offering, they are to bring a female without defect.

‘Anyone who cannot afford a lamb is to bring two doves or two young pigeons to the Lord as a penalty for their sin—one for a sin offering and the other for a burnt offering.

The Lord said to Moses: “When anyone is unfaithful to the Lord by sinning unintentionally regarding any of the Lord’s holy things, they are to bring to the Lord as a penalty a ram from the flock, one without defect and of the proper value in silver, according to the sanctuary shekel.[d] It is a guilt offering.

Why?

The Lord let sinners offer an affordable offering to erase their sins, which they had sinned unintentionally, and they had to confess their sins. If they did not confess their sins, it is meaningless to offer a sacrifice or ask for the erasing of their sins.

Here, the sins need to be erased by blood, so Jesus Chris shed the blood on the cross to erase our sins.

How?

Thank Jesus Christ shed for us, and through the trust and faith in Jesus Christ, we can be a family member of the Lord.