The Heidelberg Catechism states that “by baptism, the sign of the covenant, infants should be incorporated into the Christian church and distinguished from the children of unbelievers.” In Exodus 19, God said that Israel was to be a kingdom of priests and a holy nation. They were to be set apart from the nations to be a dedicated people to God and God alone.
God’s people always have always been known by and through their signs and symbols. The symbol, then, that affirmed this set-apart status, was the ritual of circumcision in the Old Covenant. To be a royal priest meant receiving a royal sign. This visible sign would incorporate the child into the covenant body and distinguish him from the children of unbelievers. In the Old Covenant, undergoing this ritual meant inclusion in a new nation, a new people.
This is precisely what baptism does: it activates the royal priesthood of the one being baptized. To be baptized is to be in the priesthood of this royal nation called the Church. This is the grammar of incorporation.
When a little child is marked with the Triune sign, he then begins his journey into maturing in his priesthood. And we as a church have this calling to add our voices, our love, and example to the least of these. Little priests imitate big priests.
