Ancient Israel defined being pure in three ways: (1) to be free of dirt or pollution; (2) to have no contact with anything that was unfit for a religious person to touch; (3) to be free of actions that were evil or that hurt others and went against God’s commands.

According to the Law of Moses, different things could be clean or unclean (pure or impure). People could become unclean if they had certain kinds of diseases, when they touched a dead body, or when they ate certain kinds of food like pork or certain kinds of fish. The Law told the people what to avoid so they wouldn’t become unclean (see especially Lev 11-18). It also told them how they could become clean again by waiting for a period of time and then being washed and making the right kind of sacrifice.

God’s priests also showed the people how to take care of who or what was unclean. Other people who lived in the ancient Near East believed that evil powers or spirits lived in certain kinds of animals and plants. Such beliefs may have had some influence on what the Israelites thought was unclean. Some of the nations that lived around them thought other animals, such as pigs, were holy or sacred. The Law of Moses told the Israelites not to eat or touch such animals.

Ordinary human experiences like sexual relations (Exod 19:4-15; 1 Sam 21:4), birth (Lev 12), and death (Num 6:6) were believed to involve impure powers or forces. So, for example, anyone who made contact with a dead body was impure and had to be made clean.

Once a year on the Great Day of Forgiveness all of the people were made pure. On this day, an animal was killed and its blood was sprinkled in the Most Holy Place of the tabernacle or temple. This was an offering to God as a sacrifice for the sins of the people. Another animal (a scapegoat) was driven out into the desert and carried Israel’s sins away (see Lev 16; 23:26-32; Num 29:7-11).

The early Christians understood that the sacrifice that made the people pure and clean was the death of Jesus Christ (Mark 10:45). Jesus’ blood was poured out for the forgiveness of sins (Matt 26:28), and it cleanses his people from all sin (1 John 1:7). The death of Jesus, they affirmed, makes it possible for his followers to be with God, and it makes their hearts and minds pure (Heb 10:19-22).