Hebrews 5:11-14 NIV

[11] We have much to say about this, but it is hard to make it clear to you because you no longer try to understand. [12] In fact, though by this time you ought to be teachers, you need someone to teach you the elementary truths of God’s word all over again. You need milk, not solid food! [13] Anyone who lives on milk, being still an infant, is not acquainted with the teaching about righteousness. [14] But solid food is for the mature, who by constant use have trained themselves to distinguish good from evil.