Tertullian, an early church leader known as a Patristic, wrote about an ancient tradition of giving new Christians a cup of milk. It was the practice of Christian communities around Tertullian in Northern Africa to offer “a mixture of milk and honey” to new believers immediately after their Baptism. This practice is described in his work The Crown (De Corona), written around 200 AD.
Milk for new Christians was also described by the Patristic, Jerome; whose ministry stretched from Rome to Jerusalem in 400AD. He wrote of Baby Christians being offered “milk and honey in representation of infancy.” (Liber Contra Luciferianos)
Babies need milk, but babies also need more than milk as they grow. Saint Paul encouraged the Corinthian Christians to grow up to more meaty matters in 1 Corinthians. I appreciate the JB Phillips translation of Paul's words:
I had to talk to you as unspiritual, as yet babies in the Christian life, And my practice had been to feed you, as it were, with “milk” and not with “meat”. You were unable to digest “meat.” (1 Cor. 4)
Christian Body Building requires more than milk.