Contradiction with Isaiah 1:18
Job 9:31 speaks of being plunged into filth despite efforts to cleanse oneself, while Isaiah 1:18 promises that sins, though scarlet, will be made white as snow through God's intervention.
Isaiah 1:18: Come now, and let us reason together, saith the LORD: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool.
Contradiction with Psalm 51:7
Job 9:31 suggests self-effort to cleanse leads to filth, whereas Psalm 51:7 speaks of God cleansing with hyssop and washing, resulting in purity and whiteness.
Psalm 51:7: Purge me with hyssop, and I shall be clean: wash me, and I shall be whiter than snow.
Contradiction with 1 John 1:9
Job 9:31 describes a sense of inevitable defilement, in contrast to 1 John 1:9 which assures that if we confess our sins, God is faithful to forgive and cleanse us from all unrighteousness.
1 John 1:9: If we confess our sins, he is faithful and just to forgive us [our] sins, and to cleanse us from all unrighteousness.