Job 13:2 (ESV)

2 What you know, I also know; I am not inferior to you.

Job is not less acquainted with the doctrine of retribution than his friends are. Yet he sees many obvious exceptions to this doctrine, exceptions that his friends are not taking into account.

God himself will later agree with Job on this point, that his ways are too high for humans to understand. If only Job could apply this truth to his own suffering! Instead, he will continue on the track of his friends, interpreting his suffering as punishment from God.