Chapters 17-20 holds a beautiful message about true holiness. This passage is full of details about how different Jews were to live holy in contrast to everyone around them in every aspect of the daily life of Israel.
The Food laws in 17:1-16 show what was holy and unholy and were focused on how meat was handled. After Noah was introduced to eating meat after the Flood it was an open door for ambiguity, but now that God came to live amongst the Nation in the Tabernacle, they had clarity about how to deal with meat. Christians are reminded in 1st Corinthians 11:27-30 that we have food that is holy too. The Lord’s Supper entails both flesh & blood spiritually, to remind us that it is Jesus who makes our whole life holy. Therefore we do not need to deal with the details of Levitical commands about food. Everything we eat and drink outside the Lord’s Supper is holy in the context of love and gratitude, see Romans 14:1-4.
The Sexual laws in chapters 18-19 are centered on the royal law of God in James 2:8 which is actually quoting Leviticus 19:18 & 34. Jesus said it best in Matthew 22:37-40, the first commandment is likened to the second, love God first and love others as yourself. This principle prevents us from entertaining or encouraging any and all kinds of sexual perversions and detestable alternative lifestyles. All of humanity is designed as sexual creatures and 18:1-30 was God’s way of making sure Israel’s sexuality was a bright and pure contrast from the polluted practices of pagan cultures around them in stark darkness. The fact that sexual laws (v10–21) are grouped with laws about child sacrifices (v1–5) and consulting dead ancestors (v6, 27) or cursing living parents (v9) indicates that this text is not simply about sexual lust. These are laws about building a family heritage, and doing so in holiness (v.7–8, 22–26). Remarkably, the parameters established in Lev. 18, critique the marriages of Abraham, who married his half sister, Gen. 20:12 (Lev. 18:9) and also Jacob, who took a “woman as a rival wife to her sister”, Gen. 29:1-30 (Lev. 18:18). If Israel lived Leviticus, then they wouldn’t repeat the same disastrous sins committed by their forefathers..So for Christians, “whatever you do in word or deed, do everything in the name of the Lord Jesus” (Colossians 3:17) He is the only man who ever treated people with purity and it’s only His Holiness that shapes our own, that we may become the righteousness of God, 2nd Corinthians 5:21.
The last few verses of Lev. 19 point Israel to God’s expectations on how to treat a foreigner living next door. It was one of the reasons Jesus told his disciples the parable of the Good Samaritan, Luke 10:25-37. It serves as the heart of what the chapter teaches about what it means to be holy. This significant role of holy citizenship shows how other New Testament writers regarded this passage as an important summary of the whole perfect law of liberty, Mat. 5:43, Rom. 13:9 & James 1:25.
The punishments & sentences for disobeying the Law of Moses in Leviticus were strict, sometimes even resulting in execution, 20:27. No one escapes the consequences of sin, except ultimately those who are found in Christ, who took our punishment on himself and forgives us completely. But “bearing their iniquity” in Leviticus 20:19 & Numbers 18:23 is a fact of life even for the faithful who are forgiven. Forgiveness is real and eternal, but some consequences will linger till Jesus comes. Why? Because we still live in a world where the rain falls on the righteous and unrighteous. God is fair even in forgiveness and in this He is just, Matthew 5:45.