Hebrews 5:11-14

11Of whom we have many things to say, and hard to be uttered, seeing ye are dull of hearing. 12For when for the time ye ought to be teachers, ye have need that one teach you again which be the first principles of the oracles of God; and are become such as have need of milk, and not of strong meat. 13For every one that useth milk is unskilful in the word of righteousness: for he is a babe. 14But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil.