Apostasy is having a knowledge of the truth and yet turning away from that truth. In chapter 13 we see the doom of the false prophets. The penalty to any false prophet was death. God hated idolatry and apostasy so much that the nearest of kin to the one who was found guilty was not spared. If an entire city turned to idolatry, the city was to be wholly destroyed and burned by fire.
Apostasy is raging in the world today. People who know the truth are living a lie. True, they have a form of godliness, but they are denying the power thereof. They may, very likely, be fooling man, but they cannot fool God, for God looks on the heart. I've met with people who are living a lie. They have fooled their family and friends for years, but they cannot fool a God who looks on the heart and who knows their true standing before Him. As I talk with these people, I can see that sin and guilt have destroyed them from within. Many of them have had the chastisement and judgment of God upon them because they are not honest with Him. My friend, don't invite God's judgment and chastisement upon your life; don't gamble on His mercy. Even though He is a merciful and loving God, He must chastise sin.
Chapter 14 gives instructions concerning the separation of God's people. The basis of separation was that the children of the Lord were holy people, chosen to be a peculiar people above all the nations that are upon the earth. God wanted them to be completely separated from the sinful customs of the heathen. He gave separation and distinctions in food (verses 3-21) and separation concerning pure religion (verses 22-29).
In chapter 15 the Sabbatic Year is again covered. This was every seventh year, which brought rest to the land and release from debts and obligations. Notice also an enlargement of the previous Law given in Exodus 23:10,11 and Leviticus 25:2-7.