- Ceremonial Law – Ceremonial laws do not contradict God’s nature, but they reflect it only in a very general sense. For example, he told the Israelites to have a weekly offering of “showbread.” This offering, like other offerings, showed that God is holy and worthy of worship, but the Bible does not assign any theological significance to the details of the offering. 
- Civil Law – Civil laws refer to the governing of Israel as a nation ruled by God. Since we are no longer a theocracy, these laws, while insightful, are not directly binding on us. As Romans 13 says, we must now obey our pagan government because God will work through it, too. 
- Moral Law – Moral laws are generally considered timeless, eternal, and universal, based on God’s own character, and therefore in force today.
Moral laws and ceremonial laws seem rather obvious, but it’s the Civil law category that is the most tricky. The reason behind the majority of the civil laws can be summed up in Jesus’ command to love the Lord your God with all your heart, soul, mind and strength and love your neighbors as yourself. The reason for this is the civil laws have to do with how one cares for one’s self as well as interacts with others. The goal of these laws was a healthy and thriving society. I would say this is where the food laws as well as the controversial Leviticus passages land (some would disagree). Bear with me a bit longer as I walk us through this.
Each law has a principle behind it that inspired the law. That principle is what Christians typically try to work into modern context when the exact execution of the law is no longer pertinent in the framework of their governmental setting. For example Deut 22:8 discusses the requirement to build a fence on your roof. The reason for this law was because people used their roofs as another room of the house. People went up there and did all sorts of things. Therefore to protect those that would be on your roof you were required to build a fence. The principle therefore is to look out for others in the situations where you are able to protect them. This is summed up on Jesus’ command to love your neighbors.
How about the food laws? I’m not going to go through all of them, yet the consumption of pork is the most well-known so we’ll take a look at that one. Leviticus 11:7-8 forbids the eating of pork because it is unclean. This law is one that was fulfilled by Christ as Peter shows in Acts 10:9-28. The purpose of the law however didn’t become entirely clear until more recently when we learned that pork is actually a very bad meat source as it is filled with parasites. The purpose of this law was the health of an individual as well as their family. Parasites are easily transferred between living beings therefore if one member of the household consumes something infested with parasites, the other members of the household have a high chance of being infested by parasites as well. The principle behind it is to care for one’s health as well as the health of those with whom one interacts. This is summed up on Jesus’ command to love your neighbors. People may choose to continue to consume pork even though it is not in their health benefit, but that does not nullify Leviticus 11:7’s claim that it is not in the best interest of you or those around you to eat it.
If the same rules of interpretation are applied to Leviticus 18 (I’m not limiting it to homosexual relationships, but to all sexual relationships discussed in the chapter) we see that all of these sexual relationships (let’s ignore the homosexual example for now due to its controversy) are unhealthy for a family and a society as a whole. These forms of sexual relationships break down the fabric of a family and/or a society not only in the broken trust and hurt individuals related to those that were involved in the individual act, but also if the act results in a child. We know a child that is the result of sexual relations with a close member has significantly higher chances of birth defects than other children. If the child happens to be born without any health issues, it is impossible for the child to be raised in their nuclear family as the kinds of relationships specified in Leviticus 18 are not sexual relationships inside the confines of marriage. It has been argued that children not raised in nuclear families (families consisting of their biological mother and father both living in the same home) have greater levels of psychological distress, have earlier involvement in sexual activity, and are more involved with substance abuse than those raised in their nuclear family. Therefore the principle of these laws is to prevent the degradation of families and society in general, as emotionally healthy children typically result in emotionally healthy adults, which are the cornerstone of a healthy society. As with the pork law, one can chose to engage in sexual relations with individuals mentioned in this chapter, but that does not nullify the familial and social affects that will be the result.
How does this pertain to Leviticus 20:13? The sexual relationship discussed is one covered by the discussion above as it also exists in Leviticus 18, but as Christ fulfilled the food laws he also fulfilled this law therefore no longer requiring the execution of the punishment. Nevertheless, that doesn’t change the negative ramifications of the relationship on the family or society should individuals chose to engage in such relationships.
Frank Turek wrote an interesting book entitled “Correct, Not Politically Correct; How Same-Sex Marriage Hurts Everyone” if one is interested in objectively looking at the ramifications of this controversial issue on society as a whole.
Nevertheless, “all have sinned and fallen short of the glory of God” (Rom 3:23). No one is righteous, not even one person (Rom 3:10), which is why God, in His great love and desire for all people to have a right relationship with Him, sent Jesus the Christ to pay the penalty for our sins in order that we might be cleansed and have His righteousness should we chose to recognize Him as Lord and God (For more information). No sin is greater than another in terms of its ability to separate us from God, all unrepentant sin separates us from God, whether it’s murder, sexual sin or even something as small as a “little white lie.” But God wants to restore your relationship with Him and it starts by getting to know Him and spending time in His word. Whenever I speak with anyone struggling with the do’s and don’ts of the Bible, I always recommend they get to know Jesus and let Him work out the details of their particular sins as they draw nearer to Him. He rejects no one, for some of His greatest messengers and friends were liars, murderers, thieves and prostitutes, so no matter what is in your past or present He loves you and wants a relationship with YOU!
 – http://www.gci.org/law/sabbath/moral
 – http://www.gci.org/law/sabbath/moral
 – http://www.ncbi.nlm.nih.gov/pubmed/9501363
 – Deleire, T., & Kalil, A. (2002). Good Things Come in Threes: Single-Parent Multigenerational Family Structure and Adolescent Adjustment. Demography,39(2), 393-413.