JUST BECAUSE ONE has been a Christian for many years, does not mean he is "mature..."
He may be like the person who had a been teacher for twenty-five years. When he heard about a job that would mean a promotion, he applied for the position. However, someone who had been teaching for only one year was hired instead. He went to the principal and asked why. The principal responded, "I'm sorry, but you haven't had 25 years of experience as you claim; you've had only one year's experience 25 times." During that whole time the teacher had not improved!
THOUGHT: So it may be with many Christians; they have not grown, but simply repeated their first year of spiritual life many times! (Mark Copeland)
KneEmail: "For though by this time you ought to be teachers, you need someone to teach you again the first principles of the oracles of God; and you have come to need milk and not solid food. For everyone who partakes only of milk is unskilled in the word of righteousness, for he is a babe. But solid food belongs to those who are of full age, that is, those who by reason of use have their senses exercised to discern both good and evil" (Heb. 5:12-14).