I explore Augustine's case against lying. 

Quotes:

1: Of lies are many sorts, which indeed all, universally, we ought to
hate. For there is no lie that is not contrary to truth. For, as light
and darkness, piety and impiety, justice and iniquity, sin and
right-doing, health and weakness, life and death, so are truth and a
lie contrary the one to the other. Whence by how much we love the
former, by so much ought we to hate the latter. Yet in truth there be
some lies which to believe does no harm: although even by such sort of
lie to wish to deceive, is hurtful to him that tells it, not to him
that believes it.

2: Some man will say, So then any thief whatever is to be accounted
equal with that thief who steals with will of mercy? Who would say
this? But of these two it does not follow that any is good, because
one is worse. He is worse who steals through coveting, than he who
steals through pity: but if all theft be sin, from all theft we must
abstain. For who can say that people may sin, even though one sin be
damnable, another venial? But now we are asking, if a man shall do
this or that, who will not sin or will sin? Not, who will sin more
heavily or lightly.

3. Apostle Peter had that in his heart which he had on his lips when
he denied Christ? Surely in that denial he held the truth within and
uttered the lie without. Why then did he wash away with tears the
denial which he uttered with his mouth, if that sufficed for salvation
that with the heart he believed? Why, speaking the truth in his heart,
did he punish with so bitter weeping the lie which he brought forth
with his mouth, unless because he saw it to be a great and deadly
evil, that while with his heart he believed unto righteousness, with
his mouth he made not confession unto salvation?

4. Why then do we not rout out heretics, in order to their being
caught, by the flesh committing lasciviousness in adultery, and yet
think right to rout them out by a mouth committing fornication in
blasphemy? For either it will be lawful to defend both the one and the
other with equal reason, that these things be therefore said to be not
unjust, because they were done with intention of finding out the
unjust: or if sound doctrine wills not even for the sake of finding
out heretics that we should have to do with unchaste women, albeit
only in body, not in mind, assuredly not even for the sake of finding
out heretics wills it that by us, albeit only in voice not in mind,
either unclean heresy were preached, or the chaste Catholic Church
blasphemed.

5. But he who says that some lies are just, must be judged to say no
other than that some sins are just, and therefore some things are just
which are unjust: than which what can be more absurd? For whence is a
thing a sin, but for that it is contrary to justice? Be it said then
that some sins are great, some small, because it is true; and let us
not listen to the Stoics who maintain all to be equal: but to say that
some sins are unjust, some just, what else is it than to say that
there be some unjust, some just iniquities?

6. commit not thou a great crime thine own, while thou dreadest a
greater crime of other men, for be the difference as great as thou
wilt between thine own and that of others, this will be thine own,

7. e36For if a lewd woman crave of you the gratification of her lust,
and, when you consent not, she perturbed with the fierceness of her
love should die, will chastity also be a murderer? Or, truly, because
we read, We are a sweet savor of Christ in every place, both in them
which are saved and in them which perish; to the one, indeed, a savor
of life unto life, to others a savor of death unto death; shall we
pronounce even the savor of Christ to be a murderer? But, for that we,
being men, are in questions and contradictions of this sort for the
most part overcome or wearied out by our feeling as men, for that very
reason has the Apostle also presently subjoined, And who is sufficient
for these things?

8. m37 (context of telling a lie to a man on death bed about his son who
died): Nay more: for these persons who are so enamored of this life,
that they hesitate not to prefer it to truth, that a man may not die,
say rather, that a man who must some time die may die somewhat later,
would have us not only to lie, but even to swear fasely; to wit, that,
lest the vain health of man should somewhat more quickly pass away, we
should take the name of the Lord our God in vain! And there are among
them learned men who even fix rules, and set bounds when it is a duty,
when not a duty, to commit perjury!