Chapter 19 listed every inappropriate act and sexual sin that the Canaanites did that polluted the land and caused God to detest them. Chapter 20 lists the penalties if the Israelites do the same things, up to and including the land spewing them out as well.

Leviticus 20

The LORD spoke to Moses, saying:

2 “Again, you shall say to the children of Israel ‘Whoever among the children of Israel, or of the strangers that stay in Israel, who gives any of his children to Molech, shall surely be put to death: the people of the land shall stone him with stones.

3 I will set my face against that man, and will cut him off from among his people; because he has given his children to Molech, to defile my sanctuary, and to profane my holy name.

4 And if the people of the land look the other way when any man gives his children to Molech, and do not kill him, 

5 Then I will set my face against that man, and against his family, and will cut him off, and all that prostitute themselves with Molech, from among their people.

6 The person that turns after those with familiar familiar spirits, and after wizards, to prostitute themselves with them, I will set my face against that person, and will cut him off from among his people.

7 So then sanctify yourselves, and be holy: for I am the LORD your God.

8 And you shall keep my statutes, and do them: I am the LORD who sanctifies you.

9 For every one that curses his father or his mother shall surely be put to death: he has cursed his father or his mother; his blood is on him.

10 The man that commits adultery with another man’s wife, or he that commits adultery with his neighbor’s wife, the adulterer and the adulteress shall surely be put to death.

11 The man that lies with his father’s wife has uncovered his father’s nakedness: both of them shall surely be put to death; their blood shall be on them.

12 If a man lies with his daughter-in-law, both of them shall surely be put to death: they have committed perversion; their blood shall be upon them.

13 If a man sleeps with a man, as with a woman, both of them have committed an abomination: they shall surely be put to death; their blood shall be upon them.

14 And if a man takes a wife and her mother, it is wickedness: they shall be burned with fire, both he and they; that no wickedness is found among you.

15 If a man lies with an animal, he shall surely be put to death: and you shall slaughter the animal.

16 If a woman approaches any animal, and lies down with it, you shall kill the woman and the animal: they shall surely be put to death; their blood shall be upon them.

17 If a man takes his sister, his father’s daughter, or his mother’s daughter, and sees her nakedness, and she sees his nakedness; it is a wicked thing; and they shall be cut off in the sight of their people. He has uncovered his sister’s nakedness; he shall bear his guilt.

18 If a man lies with a woman during her menstrual cycle, and uncovers her nakedness; he has uncovered her flow, and she has uncovered the fountain of her blood: and both of them shall be cut off from among their people.

19 You shall not uncover the nakedness of your mother’s sister, nor of your father’s sister: for he uncovers his near kin: they shall bear their iniquity.

20 If a man lies with his uncle’s wife, he has uncovered his uncle’s nakedness: they shall bear their sin and shall die childless.

21 If a man shall take his brother’s wife, it is an unclean thing: he hath uncovered his brother’s nakedness; they shall be childless.

22 You shall keep all my statutes, and all my judgments, and do them: that the land, that I bring you to to dwell in, does not spew you out.

23 You shall not walk in the manner of the nation that I cast out before you: for they committed all these things therefore I detest them.

24 But I have said to you “You shall inherit their land, and I will give it to you to possess it, a land that flows with milk and honey: I am the LORD your God, which has separated you from other people.”

25 You shall therefore distinguish between clean animals and unclean, and between clean and unclean birds: and you shall not make your souls defiled by animals, or by birds, or by any manner of living thing that creeps on the ground, which I have separated from you as unclean.

26 You shall be holy to me: for I the LORD am holy, and have separated you from other people, that you should be mine.

27 If a man or woman has a familiar spirit, or is a wizard, they shall surely be put to death: you shall stone them with stones: their blood shall be upon them.'”

See also: Leviticus 20 in ESV, HCSB, NASB and NIV via Bible Gateway.