Modern Western people may find it difficult to understand the Old Testament laws of purity. Today, things like skin diseases, bodily discharges, or contact with a dead body are viewed mainly as health concerns. But in the Old Testament, the main concern was protecting God’s holiness from ceremonial uncleanness (see Leviticus 11–15).
The community had to keep the camp holy. Nothing unclean could touch what belonged to the Lord (Numbers 5:2–3). They had to choose between having God in the camp or allowing a ceremonially polluted person stay. Both could not remain (5:3).
The importance of purity continues from Leviticus and Numbers to the book of Revelation. Nothing ceremonially unclean will enter the New Jerusalem where God lives (see study note on Revelation 21:27). In the New Testament, impurity most often refers to what is morally impure (Acts 10:28; Ephesians 5:5; 1 Thessalonians 2:3; 4:7).