Thematic Bible: Who is immature

So I myself, brothers, could not deal with you as spiritual persons, but as creatures of human clay, as merely baby Christians. I fed you with milk, not solid food, for you could not take it. Why, you cannot take it even now, for you are still unspiritual. For when there are still jealousy and wrangling among you, are you not still unspiritual and living by a human standard?

I have much to say to you about Him, but it is difficult to make it clear to you, since you have become so dull in your spiritual senses. For although you ought to be teachers of others because you have been Christians so long, you actually need someone to teach you over and over again the very elements of the truths that God has given us, and you have gotten into such a state that you are in constant need of milk instead of solid food. For everyone who uses milk alone is inexperienced in the message of right-doing; he is only an infant.