And he took bread, and when he had given thanks, he broke it and gave it to them, saying, “This is my body, which is given for you. Do this in remembrance of me.” And likewise the cup after they had eaten, saying, “This cup that is poured out for you is the new covenant in my blood.” Luke 22:19-20
I still remember when I took my test to get my driver’s permit. I waited in the long DMV line took the test and brought it back up to the lady at the counter. She looked at me and said, “You didn’t answer a question.” I replied, “Is it going to matter?” “Yes.” She gave me the test back and I proceeded to get the wrong answer and failed my permit test. I finally grabbed the study booklet and started to review the meaning of all the various signs one sees on the road in the hopes of passing the test. Each sign I studied was a symbol for what drivers needed to know in order be aware of their surroundings.
Signs are powerful tools to protect people from dangers as well as to encourage them that they are traveling in the right direction. The Lord Jesus has given His people two signs for the Christian gospel: Baptism and the Lord’s Supper. Both these signs were commanded by Jesus Christ during His earthly ministry. These signs are known as ordinances. These two ordinances are signs both to the church community and to the world of who has identified themselves with Christ death and resurrection.
Baptism is the sign symbolizing one has entered into a relationship with Jesus Christ. Individuals are buried under the water to identify with Christ’s death and are raised out of the water to identify with Christ’s resurrection. This is an outward symbol of an inward change. The Lord’s Supper is a sign symbolizing that one is continuing in their relationship with Jesus Christ. The bread and cup represent Christ’s broken body and His shed blood. In partaking of the Lord’s Supper you are showing you have communion with God and with His people.
These two ordinances are signed to distinguish between God’s people and the world. As Timothy Keller says they are, “boundary markers,” for the covenant church community. Baptism is a sign you are now a part of the church while the Lord’s Supper is a sign that you are still a part of the church. These signs protect the church’s membership and clarify to the world who is and who is not part of God’s people. Therefore, these signs make the gospel visible to the church and to the world. I pray that when you see these signs, your, “seeing leads to believing.”
 J.I. Packer quoted by Tim Keller in New City Catechism Question 43.
image credit (http://www.jigzone.com/p/jz/p13/Road_signs.gif)