Hebrews 5:11-12

11Concerning this we have much to say, and it is hard to explain, since you have become dull and sluggish in [your spiritual] hearing and disinclined to listen.

12For though by this time you ought to be teachers [because of the time you have had to learn these truths], you actually need someone to teach you again the elementary principles of God’s word [from the beginning], and you have come to be continually in need of milk, not solid food.