Job 36:4

For truly my words [shall] not [be] false
But strictly true; he would take the utmost care to say nothing but the truth, with the greatest impartiality and sincerity, so that what was said might be depended upon; truth spoken briefly, clearly, and on so important a subject as the righteousness of God, deserved attention;

he that is perfect in knowledge [is] with thee;
meaning either God, whose knowledge is perfect, who knows all persons and things; knows himself, his nature, persons, and perfections; his thoughts, counsels, and purposes; all his creatures, angels and men; the hearts of all men, their thoughts, words, and works; he, the omniscient and omnipresent God was with Job, from whose presence there is no fleeing; and therefore it became him to be careful of his thoughts, words, and actions; that he did not entertain any unbecoming thoughts of God, and say anything unworthy of him, or do anything that tended to his dishonour; since he was present with him, and nothing could escape his notice: or else Elihu means himself; suggesting, that he who undertook to speak for God and plead his cause, and clear him from the charge of unrighteousness, was no novice, but one that thoroughly understood the point in hand; and though no man is perfect in knowledge in an absolute sense, yet may be in comparison of others; or however may be upright and sincere in his knowledge; which sense the word used often has; and so it may signify, that as he was a sincere searcher after knowledge, and had through divine goodness attained to a competent share of it, even of sound and not superficial knowledge, he should be honest and upright in the communication of it; and this he might choose to observe the more, to excite the attention of Job to what he had to say; though it may be the truest reading of the words is, "perfect knowledge" or "perfection of knowledge is with thee" ^F11, that is, in his own apprehension, so Jarchi; and may be understood either ironically, or rather really, insinuating that Job was a man of such consummate wisdom and knowledge, that he would easily see the force of his reasonings, and the justness of them, and acquiesce in them; and having thus prefaced his discourse, he next enters upon his subject.