1 Corinthians 3:2

2. With milk… meat By these terms is not meant the easier and the harder doctrines of theology, as foreknowledge and predestination, resurrection, etc. These are easily intelligible by the logical understanding to those who are not even babes in Christ, but are unregenerate. Paul refers to the principles of the lower and the higher Christian life. Milk is the doctrine of repentance, of avoiding sin, while meat represents those higher views of the spiritual (1 Corinthians 2:14-16) which the carnal could not receive, such as deep communion with God, profound purity of conscience, and the utter consecration of all to holiness and God.

Yet now This entire epistle, as to babes, deals almost exclusively with the principles of Christian ethics and doctrine; whereas that to the Ephesians, as to spiritual, mounts to the very heights of Christian spirit and life.