1 Corinthians 3:1, 18, 21
1 Corinthians 3:1 ESV
But I, brothers, could not address you as spiritual people, but as people of the flesh, as infants in Christ.
1 Corinthians 3:18 ESV
Let no one deceive himself. If anyone among you thinks that he is wise in this age, let him become a fool that he may become wise.