One reason that the ordinances seem weird to us is that we have trouble believing that what we do in the body matters. There is plenty of mental and verbal pieces to our spiritual lives. We’re people who love prayer and Bible reading and singing and meditating on the law of the Lord. But while the Word explains the significance of the sacraments, the Word does not replace their blessings.
Baptism is a symbol of an invisible change; we have died, been buried, and were raised to walk in newness of life. The spiritual reality is represented externally. The physical act is visible. Likewise, with communion, the greatest thing we could ever think about–the love of God in the sacrifice of Christ on behalf of His sheep–God wants us to do more than think about. He wants us to eat.
Which is sort of surprising. Men keep messing up their desire for and use of food. In John 6, the crowd followed Him and wanted to make Him King because He had feed ten to fifteen thousand people from a few loaves and fish. He offered them a food that endures to eternal life. Wouldn’t it have been beneficial for Him to talk about it as something other than bread? When it came time to institute the Lord’s supper, why didn’t He choose something else that was clearly special, something sacred? The Corinthians abused it too, and Paul said, “When you come together, it is not the Lord’s supper that you eat.” But what makes the difference? It wasn’t the type of bread or wine. It was their attitude toward and use of the normal bread and wine before them.
God could have come up with any number of other ways to commemorate the good news of Christ giving His body and shedding His blood for sinners. But He took our common experience and transposed it. By faith we share mystical union with God and with each other through the earthly, material, ordinary bite of bread and swallow from a cup.