Augustine of Hippo

And when we confess that we have lied, we speak the truth, for we are saying what we know, and we know that we have lied. That Word, however, which is God and more powerful than ourselves, cannot do this.… And of himself he does not speak, but of that Father is everything that he speaks, since the Father speaks it in a unique way. The great power of that Word is that he cannot lie, because in him there cannot be yes and no but yes, yes; no, no. For that is not even to be called a word if it is not true.