The operative word here is יָכַח (yakach) - a word occurring 59 times in the OT, meaning "decide, adjudge, prove' according to BDB.
In Job 13:15 it is variously translated as, defend, argue, plead, reprove, maintain my ways, etc. All of these are correct. It is one of the great characteristics of YHWH God He encourages debate, discussion to further understand Him. As evidence of this note the following:
- Isa 1:18 - “Come now, let us reason together,” says the LORD.
- The Psalms in hundreds of places have people questioning God who is always patient with such questions
- Rom 3:4 ... As it is written: “That You may be justified in Your words, And may overcome when You [God] are judged.”
However, Job realised he was a sinner as recorded later in the same chaper of Job 13:
V23: How many are my iniquities and sins? Reveal to me my
transgression and sin. (See appendix below)
Job's great HOPE is recorded in Job 19:23-27 -
I wish that my words were recorded and inscribed in a book, by an iron
stylus on lead, or chiseled in stone forever. But I know that my
Redeemer lives, and in the end He will stand upon the earth. Even
after my skin has been destroyed, yet in my flesh I will see God. I
will see Him for myself; my eyes will behold Him, and not as a
stranger. How my heart yearns within me!
Thus, Job has three great characteristics:
- He realized he was a sinner (although not as great as his "punishment" implied)
- He wanted to question and debate with God to better understand Him
- He earnestly yearned and hoped for the resurrection
APPENDIX - Comments on Job 13:23 -
(23) How many are mine iniquities?—We must be careful to note that
alongside with Job’s claim to be righteous there is ever as deep a
confession of personal sin, thus showing that the only way in which we
can understand his declarations is in the light of His teaching who
convicts of sin before He convinces of righteousness.
Job 13:23-24. How many are my sins? — That I am a sinner, I confess;
but not that I am guilty of such crimes as my friends suppose; if it
be so, do thou, O Lord, discover it. Wherefore hidest thou thy face? —
Withdrawest thy favour and help, which thou hast been wont to afford
me; and holdest me for thine enemy? — That is, dealest as sharply with
me as if I were thy professed enemy.