Hebrews 5:12-14 (KJV) "For 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. For every one that useth milk is unskilful in the word of righteousness: for he is a babe. But 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."

Proverbs 27:17 (KJV) "Iron sharpeneth iron; so a man sharpeneth the countenance of his friend."