17. Speaketh truth. Literally, “breatheth out truth.” Perhaps a reference to the confirmed habit of speaking truth, that is, a man speaks truth as naturally as he breathes. The one with such a trait of character is governed by the dictates of right (MB 104, 105). It is for this reason that Christians need have no hesitation in taking the judicial oath (see MB 104, 105; DA 706, 707).
On the contrary, the habitual prevaricator does not tell the truth even when he swears to do so. His habit of suppressing part of the truth, or coloring it until it gives an impression that is really a lie, will soon show the observant listener that no credence can be placed in his word (see 14:5, 25).