Job 27:4

My lips shall not speak wickedness
This is the thing he swears to, this the matter of his oath, not only that he would not speak a wicked word not anything corrupt, unsavoury, unchaste, profane, and idle nor speak evil of his neighbours and friends or of any man; but that he would not speak wickedly of himself, as he must do, if he owned himself to be a wicked man and an hypocrite as his friends charged him, and they would have had him confessed; but he swears he would not utter such wickedness as long as he had any breath in him:

nor my tongue utter deceit;
which respects the same thing; not merely any fallacy or lie, or what might impose upon and deceive another, which yet he was careful of; but such deceit and falsehood as would be a belying himself, which would be the case should he say that he was devoid of integrity and sincerity.