The Lord Jesus said to a religious leader of His day: “Except a man be born again he cannot see the kingdom of God” (John 3:3). All true Christians have been born again by the Spirit of God (Titus 3:5). They are therefore the children of God (Rom. 8:16).
Children are a joy in any normal household, but it is a tragedy when a child remains a child, physically, mentally or both. It is a tragedy too, that so many Christians, truly born again, remain spiritual babes — they do not grow. They know that Christ died for their sins but have made no progress in grace or in the knowledge of the Word. To such Paul wrote:
“And I, brethren, could not speak unto you as unto spiritual [men], but as unto carnal, even as unto babes in Christ. I have fed you with milk, and not with meat; for hitherto ye were not able to bear [digest] it, neither yet now are ye able” (I Cor. 3:1,2).
Thus those who, spiritually undeveloped, were able to digest only the milk, or the simple things, of the Scriptures, were called “carnal” and “babes,” in contrast to those “spiritual” believers who had grown in grace and were able to assimilate the deeper, richer truths of the Word of God.
This is not a compliment to those who constantly boast that they are satisfied with “the simple things,” and fail to study God’s Word, as II Tim. 2:15 commands. To such Paul writes, by divine inspiration:
“For when for the time ye ought to be teachers, ye have need that one teach you again… and are become such as have need of milk… For every one that useth milk is unskilful in the Word of righteousness, for he is a babe. But strong meat [solid food] belongeth to them that are of full age…” (Heb. 5:12-14). source