Albert Barnes Commentary Job 36:4

"For truly my words are not false: One that is perfect in knowledge is with thee." — Job 36:4 (ASV)

For truly my words shall not be false - This is designed to gain attention. It is a stated purpose to state nothing but truth. Even in order to vindicate the ways of God, he would state nothing but what would withstand the most rigorous examination. Job had charged his friends with a purpose to speak wickedly for God; to make use of unsound arguments in vindicating His cause (see the notes at Job 13:7-8), and Elihu now says that he will make use of no such reasoning, but that all he says will be founded on strict truth.

He that is perfect in knowledge is with thee - This refers undoubtedly to Elihu himself and is a claim to a clear understanding of the subject. He did not doubt that he was right and that he had some views which were worthy of their attention. The main idea is that he was of sound knowledge; that his views were not sophistical and captious; that they were founded on truth and were worthy, therefore, of their profound attention.