Hebrews 5:12-13

For even though by this time you ought to be teaching others, you actually need someone to teach you over again the very first principles of God's Word. You have come to need milk, not solid food. For everyone who continues to feed on milk is obviously inexperienced and unskilled in the doctrine of righteousness (of conformity to the divine will in purpose, thought, and action), for he is a mere infant [not able to talk yet]!