From RJ Rusdoony:

When a person was baptized in the early church, and I cite this from Walter Oetting, The Church of the Catacombs, again an out of print work from 1964. When someone was baptized, they were immediately given milk and honey, to symbolize that they were babes in Christ, but also to show that they were now in the Promised Land, the land flowing with milk and honey. As a result, just as Moses and Joshua told the Israelites, the land before you is a land flowing with milk and honey, go in and possess it. So the new convert was told: “You are now a new creation, and the world before you is the new kingdom, the promised land, and you are to go in and possess it.”

Let me quote a statement on this very briefly from Hippolytus, one of the early church fathers: “And milk and honey mixed together for the fulfillment of the promise to fathers, which spoke of a land flowing with milk and honey, namely Christ’s flesh which He gave, by which they who believe are nourished by faith; he making sweet the bitter things of the heart by the gentleness of his word.”

The milk and honey therefore was an important part of the service of the early church whereby a Christian became a Christian, was baptized into the faith.