A common argument against Christianity by many atheists is the idea that Christians don't follow the dietary laws of the Old Testament. I recently heard one ask, "Why are you not firebombing Red Lobster restaurants for serving shellfish?" and "Why are you not calling for the dissolution of clothing companies that produce garments of mixed fabrics?"

The question being asked is a good one, but it shows a common misunderstanding about the role and purpose of Jesus, known as the Messiah.

Before we specifically address the question of shellfish, I would ask as easier question: why do you think Christians no longer participate in the Old Testament sacrifice of animals in the Temple?

The transition from the sacrificial system of the Old Testament to its fulfillment in Jesus Christ provides a solid foundation for understanding why Christians no longer adhere to certain Old Testament practices.

The Old Testament Levitical sacrifices were a significant aspect of God's law for the Israelites. These sacrifices were given by God as a means for His people to atone for their sins and maintain their covenant relationship with Him. However, these sacrifices were insufficient and always intended to point towards something—or rather, Someone—greater.

In the book of Hebrews, the author spends significant time exploring this shift. In Hebrews 10:1, we read, "For since the law has but a shadow of the good things to come instead of the true form of these realities, it can never, by the same sacrifices that are continually offered every year, make perfect those who draw near." The repeated sacrifices of the Old Testament were, in a way, a reminder of sin and an anticipation of the coming redemption.

That redemption arrived in the person and work of Jesus Christ. He is described as the ultimate high priest and the perfect sacrifice in one. Hebrews 10:10 says, "And by that will, we have been made holy through the sacrifice of the body of Jesus Christ once for all." Christ's death on the cross was the fulfillment of the sacrificial system. His sacrifice was sufficient to atone for all the sins of those united to Him, rendering the repeated sacrifices of the Old Testament no longer necessary.

This critical shift extends beyond the sacrifices and encapsulates other elements of the law, including dietary regulations and rules about clothing. Like the sacrifices, these laws were also pointers, ways of setting the Israelites apart from other nations and reminding them of their unique relationship with God. With the coming of Christ, these laws found their fulfillment as the Gentiles are now ingrafted into the covenant community. God's people are now defined not by external observance of the law, but by faith in Christ.

Therefore, just as we understand that the Old Testament sacrifices are no longer necessary due to their fulfillment in Christ, so too can we understand that the laws regarding diet and clothing have found their completion in Him. They served their purpose under the old covenant, but under the new covenant, we are no longer bound by their specific requirements.

The apparent critique of Christians' non-adherence to certain Old Testament laws, such as dietary restrictions or textile regulations, is one to be further addressed with careful consideration of some Biblical texts.

Let's take a look at Acts 10, wherein we find the apostle Peter's vision from God after the resurrection of Jesus. In this vision, a sheet descends from heaven containing all manner of creatures - many of which are explicitly labelled "unclean" in the Mosaic law. Yet, the voice of God commands Peter to rise, kill, and eat these creatures. Peter, an observant Jew, objects, noting that he has never consumed anything unclean. In response, God declares, "What God has made clean, do not call common."

The declaration signifies not just a change in dietary rules, but a profound theological shift. It anticipates the meeting between Peter and Cornelius, a Gentile - the inclusion of Gentiles among God's chosen people is a theme that reverberates throughout the New Testament, and is in fact symbolized in the dismissal of the dietary laws.

God clearly and vividly illustrated that the legal distinction between what is clean and unclean has been done away with, suggesting that the barrier that once separated Jews and Gentiles has been demolished. This metaphorical barrier is symbolically represented by the dietary laws among other Old Testament laws.

The Apostle Paul echoed this sentiment by declaring a once hidden mystery: Gentiles, who were once considered outside the covenant, can now partake in the same salvation offered to the Jewish people. They are no longer excluded or separate, but are now grafted into the same body of believers, a unified church that transcends ethnic and cultural divisions.

These biblical truths are reflected in his letters to the Ephesians (2:16; 3:6), where he writes of how both Jews and Gentiles are reconciled into one body through the cross, abolishing in his flesh the law with its commandments and regulations. And in the mystery of Christ, the Gentiles are heirs together with Israel, members together of one body, and sharers together in the promise in Christ Jesus.

Therefore, the shift from Old Testament dietary and fabric laws to the teachings of the New Testament isn't a contradiction, but rather a manifestation of a greater plan. A plan in which the gospel is for all people, regardless of their ethnicity or cultural heritage, unified in Christ. So, the New Testament believers' practices, including the consumption of shellfish and wearing of mixed fabrics, are a testament to this newfound liberty and unity in Christ. They are visible signs of a heart transformed by the grace of the gospel and a life marked by the Spirit's work, rather than the outward adherence to the ceremonial laws of the Old Testament.

Romans 7:1-6 provides a vivid metaphor to illustrate the transition from the Old Covenant to the New Covenant in Christ. The Apostle Paul compares the Old Testament law to a marriage covenant, where we were bound to our spouse (the law) as long as we lived. However, when that spouse dies, we are released from the law of the marriage. In the same vein, through Christ's death and resurrection, we have metaphorically 'died' to the law. This death has released us from the binding demands and penalties of the law, akin to a widow being released from her marriage obligations. But the analogy doesn't stop there. Paul goes on to say that we now 'belong to another'. This is a reference to our new union with Christ. We're not left as widows, but remarried—to Him who was raised from the dead. Our relationship to the law has fundamentally changed; we are no longer under its condemnation but live under the grace and liberty of our new 'marriage' to Christ.

Moreover, Jesus Himself in Mark 7:18-19 declared all foods clean. He challenges the Pharisees' preoccupation with external cleanliness, implying that what defiles a person comes from the heart, not from what they eat.

In regards to wearing garments of mixed fabric, it's essential to understand the historical and symbolic significance of this command. The law found in Leviticus 19:19 was given to the Israelites to set them apart from surrounding nations, as a physical reminder of their unique covenant relationship with God. However, under the New Covenant in Christ, this external symbol of separation is no longer necessary. As Galatians 3:28 states, "There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus."

Thus, the Christian is not bound by these Old Testament restrictions because they have been superseded by the New Covenant in Christ. His work has not dismissed the law, but rather fulfilled it, rendering the literal observance of these laws obsolete while preserving their spiritual essence. In Christ, we are all made clean, and the external symbols that once set God's people apart are no longer needed. It is a heart turned toward God, not diet or dress, that now signifies belonging to His covenant people.