The Desire to Tell the Truth

Among the Propensive tendencies may properly be reckoned the principle of Veracity; that is to say, the disposition, which is evidently natural to the human mind, to utter the truth. It would not be easy to exaggerate the importance of this principle; but it is well known, that there are influences at work, originating in selfishness and in unbelief, which frequently pervert its action. But if unbelief is the enemy of the correct action of this important principle; faith, on the other hand, is its strong friend. 

I think that it is one of the striking evidences of a man of strong faith, that he both speaks the truth, and has confidence in the truth. In his intercourse with men, he does not speak rudely and unkindly, but he tells his simple, unvarnished story in a simple and true spirit. “His yea is YEA, and his nay, NAY.” He may sometimes speak with emphasis; but never with exaggeration. He may regard, as he ought to regard, the proprieties both of language and of manner; but he cannot, as a man of true faith in God, attach to his statements any embellishments of word or any devices of action, which will alter, even slightly, the aspect of the reality of things. 

And accordingly, believing in God as a God, who has declared of himself, that he cannot lie, and deeply desirous of bearing the divine image in this respect as well as in other respects, he utters his words in humble but unchangeable sincerity and uprightness; and although he is conscious that they are unsustained by the artifices of unbelief, he knows equally well who will make them good in the end.

— edited from The Life of Faith, Part 2, Chapter 5.