In the Lord’s Supper we eat and drink in remembrance of the risen and reigning Lord Jesus, who is present with us. In the meal, we’re confirmed in our identity as God’s covenant people and renew our commitment to trust and obey him. The Lord’s Supper is a perpetual proclamation of the Gospel and anticipation of Jesus’ Second Coming.
God made the rainbow a sign of his covenant that he would never again flood the Earth. Since this sign is visible to all peoples everywhere and through all times then everyone is included in God's covenant and is subsequently either a covenant-keeper or a covenant-breaker.