There are lots of diets out there in our world today. Atkins Diet, Grapefruit Diet, South Beach...Most of them telling you what you should and shouldn't eat. My favorite diet is the Seafood Diet - if you see food you eat it!
In the OT God put His people Israel on a diet. He actually had a pretty extensive list of dietary restrictions for them. They included - only animals that chew the cud and have cloven hoofs; only non-scavenger birds; only fish with fins and scales; no insects except locusts; milk and meat could not be mixed; all blood must be removed; and the animal must be butchered in a humane manner. Eating things like pork and shellfish and certain other foods weren't permitted.
Some believe God’s list of approved and forbidden foods were about health considerations.
While that may be part of it, more importantly, this was one of the ways God used to mark or set apart those whom He had chosen. God didn't pick Israel because they were better people, smarter, more powerful, or more promising. They were nobodies, and yet God chose them anyway. Observance of food laws became one of the outward signs of being an Israelite, and served as a reminder of their status as people who were set-apart for God's purpose.
While this was a good thing, problems began to arise when the people started thinking they could be clean before God simply by what they did or what they didn't do - by washing their hands, or by eating or not not eating certain things. But that wasn't the point - they were missing the heart of the matter.
"Jesus called the people to him and said, "Nothing outside of you can defile you by going into you. Rather, it is what comes out of you that defiles you." Jesus is telling us that the kind of food you eat doesn’t matter nearly as much as the kind of person you are. And it’s not what you come in contact with from the outside that makes you unclean, but what comes out of you. It comes from the inside out. What Jesus is saying is that our root problem of sin isn't caused by our environment, by the way we were raised, the culture we’re in, or anything else outside of us. He is saying that its caused by what’s inside of us - our sinful human nature, inherited from Adam, which resides within the heart of each and every human being.
The problem with the Pharisees is that they were trying their own outside-in approach to solve the sin problem. They thought that sin could be rooted out by doing outward actions, religious rituals, washing your hands, watching what you eat, etc.
And while its true that we need an outside-in approach to solve our sin problem, its not the kind the Pharisees were focusing on, and its certainly not the kind the religions of the world offer us today. The kind we need, the only one that works, is the approach that God offers us in His Word. And that is for God to come from the outside in, in order to change us from the inside out.
So God sent His one and only Son, Jesus down from heaven to earth to fulfill the law through His perfect life and by His sacrificial death. He came to set us free from the demands of the law, in order to make us clean in the eyes of God through His blood shed for us on the cross.
The substance behind the shadow of the law has now been revealed in the Gospel of Jesus Christ. Everything the OT pointed forward to has now been fulfilled in Him. No longer can a dead body, an animal carcass, or a pulled pork sandwich make a person unclean anymore.
Praise be to God for that!
Because Christ has come, because Messiah is here, the purity laws associated with the OT law are no longer binding on God’s people. Its not that they were wrong - they played an important role among God’s people for a set period of time. But now that Messiah has come, now that the Kingdom of God is here and has been opened for all people, those purity laws are now obsolete.
You see, Jesus didn't come to abolish the law, but to fulfill it. Though God's moral laws do not change, the dietary codes are not binding on us. We are no longer bound by the Old Testament civil and ceremonial laws. We’re free to eat or not eat certain foods, to observe or not observe certain customs - That's the freedom we now have in the Gospel. Thanks be to God that in Christ we are free to live under His grace, since He has come to change us from the inside out.