In I Corinthians 3:1-3 (NRSV), Paul told Christians who were members of the church at Corinth that he wasn’t able to feed them with solid food because they weren’t ready for it. Why? They acted like people of the flesh rather than spiritual people. Why? The church continued to have divisions in it. Accordingly, they were “infants in Christ,” requiring that they be fed with milk.
Paul’s metaphor has been used ever since to distinguish the spiritual maturity between newly converted Christians and long-time members of the faith. But not all long-time believers are mature (in the way Paul described maturity), and not all Christians who are sustained by milk are weak or immature.
Remember that Jesus told his disciples to let little children come to him, “for the kingdom of heaven belongs to such as these.” (Matthew 19:14, NIV) Moreover, in I Peter 2:2-3 (NRSV), Peter gave Christians this message: “Like newborn infants, long for the pure, spiritual milk, so that by it you may grow into salvation — if indeed you have tasted that the Lord is good.” Interestingly, just as newborn babies long for nurturing milk, Christians should long for spiritual milk, because it allows growth “into salvation” and is a sign that believers have tasted the Lord’s goodness.
Sometimes, new Christians are much more in tune with the unity of Christ’s church than old-line Christians who’ve closed their minds to unity because they alone know the truth. They don’t sound like Jesus’ little children who are still growing and learning and maturing. It may be that the solid food Paul described is the same as the spiritual milk Peter described. The scripture in I Corinthians 3 and I Peter 2 holds up maturity and growth but recognizes that they are attained through a spiritual focus on unity, salvation, and goodness.