Albert Barnes Commentary Job 31:5

"If I have walked with falsehood, And my foot hath hasted to deceit" — Job 31:5 (ASV)

If I have walked with vanity — This is the second specification in regard to his private deportment. He says that his life had been sincere, upright, honest. The word "vanity" here is equivalent to falsehood, as the parallelism demands, and as the word (שׁוא shâv') is often used (Psalms 12:3; Psalms 41:7; Exodus 23:1; Deuteronomy 5:20; compare Isaiah, Deuteronomy 1:13).

Job's meaning here is that he had been true and honest. In his dealings with others, he had not defrauded them; he had not misrepresented things; he had spoken the exact truth, and had done that which was without deception or guile.

If my foot hath hasted to deceit — That is, if I have gone to execute a purpose of deceit or fraud. He had never, on seeing an opportunity where others might be defrauded, hastened to embrace it. The Septuagint renders this verse: If I have walked with scoffers — μετα γελοιαστῶν meta geloiastōn — and if my foot has hastened to deceit.