Every believer, at salvation, is born into the family of God. But a baby grows up, matures, becomes a man, and takes on responsibility. As it is in the natural, so it is in the spiritual.
Scripture cites two basic evidences of spiritual infancy.
Even so we, when we were children, were in bondage under the elements of the world. B. Inability to discern or understand doctrine. Them that are weaned from the milk, and drawn from the breasts. The Word of God gives growth to our spiritual lives. A. Milk is for the babes.