Purgatory

Accordingly the believer, through great discipline, divesting himself of the passions, passes to the mansion which is better than the
former one, viz., to the greatest torment, taking with him the characteristic of repentance from the sins he has committed after baptism.
He is tortured then still more--not yet or not quite attaining what he sees others to have acquired. Besides, he is also ashamed of his
transgressions. The greatest torments, indeed, are assigned to the believer. For God's righteousness is good, and His goodness is
righteous. And though the punishments cease in the course of the completion of the expiation and purification of each one, yet those
have very great and permanent grief who are found worthy of the other fold, on account of not being along with those that have been
glorified through righteousness.

CLEMENT OF ALEXANDRIA, The Stromata, Book 6, Chapter 14 [A.D. 188-199]

Now the friendly understanding you will have to carry out must arise from your observance of the compact: you must never think of
getting back any of the things which you have abjured, and have restored to him, lest he should summon you as a fraudulent man, and
a transgressor of your agreement, before God the Judge (for in this light do we read of him, in another passage, as "the accuser of the
brethren," or saints, where reference is made to the actual practice of legal prosecution); and lest this Judge deliver you over to the
angel who is to execute the sentence, and he commit you to the prison of hell, out of which there will be no dismissal until the smallest
even of your delinquencies be paid off in the period before the resurrection. What can be a more fitting sense than this? What a truer
interpretation?

TERTULLIAN, A Treatise on the Soul, Chapter 35 [A.D. 200]

... how much more will one who, neither by her own nor her husband's fault, but by an event resulting from the Lord's law, has been--
not separated from, but left behind by--her consort, be his, even when dead, to whom, even when dead, she owes (the debt of)
concord? ...Indeed, she prays for his soul, and requests refreshment for him meanwhile, and fellowship (with him) in the first
resurrection; and she offers (her sacrifice) on the anniversaries of his falling asleep.

TERTULLIAN, On Monogamy, Chapter 10 [A.D. 200]

And do not think, dearest brother, that either the courage of the brethren will be lessened, or that martyrdoms will fail for this cause,
that repentance is relaxed to the lapsed, and that the hope of peace is offered to the penitent. The strength of the truly believing
remains unshaken; and with those who fear and love God with their whole heart, their integrity continues steady and strong. For to
adulterers even a time of repentance is granted by us, and peace is given. Yet virginity is not therefore deficient in the Church, nor does
the glorious design of continence languish through the sins of others. The Church, crowned with so many virgins, flourishes; and
chastity and modesty preserve the tenor of their glory. Nor is the vigour of continence broken down because repentance and pardon
are facilitated to the adulterer. It is one thing to stand for pardon, another thing to attain to glory: it is one thing, when cast into prison,
not to go out thence until one has paid the uttermost farthing; another thing at once to receive the wages of faith and courage. It is one
thing, tortured by long suffering for sins, to be cleansed and long purged by fire; another to have purged all sins by suffering. It is one
thing, in fine, to be in suspense till the sentence of God at the day of judgment; another to be at once crowned by the Lord.

CYPRIAN, Epistle 51 To Antonianus, Chapter 20 [A.D. 200-258]

Then we commemorate also those who have fallen asleep before us, first Patriarchs, Prophets, Apostles, Martyrs, that at their prayers
and intercessions God would receive our petition. Then on behalf also of the Holy Fathers and Bishops who have fallen asleep before
us, and in a word of all who in past years have fallen asleep among us, believing that it will be a very great benefit to the souls, for
whom the supplication is put up, while that holy and most awful sacrifice is set forth. ...

...And I wish to persuade you by an illustration. For I know that many say, what is a soul profited, which departs from this world either
with sins, or without sins, if it be commemorated in the prayer? For if a king were to banish certain who had given him of-fence, and
then those who belong to them 155 should weave a crown and offer it to him on behalf of those under punishment, would he not grant
a remission of their penalties? In the same way we, when we offer to Him our supplications for those who have fallen asleep, though
they be sinners, weave no crown, but offer up Christ sacrificed for our sins, propitiating our merciful God for them as well as for
ourselves.

CYRIL, Lecture 23:9,10 [A.D. 315-386]

The same divine fire, therefore, with one and the same force and power, will both burn the wicked and will form them again, and will
replace as much as it shall consume of their bodies, and will supply itself with eternal nourishment: which the poets transferred to the
vulture of Tityus. Thus, without any wasting of bodies, which regain their substance, it will only burn and affect them with a sense of
pain. But when He shall have judged the righteous, He will also try them with fire. Then they whose sins shall exceed either in weight
or in number, shall be scorched by the fire and burnt: but they whom full justice and maturity of virtue has imbued will not perceive that
fire; for they have something of God in themselves which repels and rejects the violence of the flame.

LACTANTIUS, The Divine Institutes, Book 7 [3rd Century]

Let us then give them aid and perform commemoration for them. For if the children of Job were purged by the sacrifice of their father,
why dost thou doubt that when we too offer for the departed, some consolation arises to them? since God is wont to grant the petitions
of those who ask for others. And this Paul signified saying, "that in a manifold Person your gift towards us bestowed by many may be
acknowledged with thanksgiving on your behalf." (2 Corinthians chapter 1, verse 11) Let us not then be weary in giving aid to the
departed, both by offering on their behalf and obtaining prayers for them: for the common Expiation of the world is even before us.
Therefore with boldness do we then intreat for the whole world, and name their names with those of martyrs, of confessors, of priests.
For in truth one body are we all, though some members are more glorious than others; and it is possible from every source to gather
pardon for them, from our prayers, from our gifts in their behalf, from those whose names are named with theirs. Why therefore dost
thou grieve? Why mourn, when it is in thy power to gather so much pardon for the departed?

JOHN CHRYSOSTOM, Homily on 1st Corinthians, 41:8 [A.D. 347-407]

After his departure out of the body, he gains knowledge of the difference between virtue and vice, and finds that he is not able to
partake of divinity until he has been purged of the filthy contagion in his soul by the purifying fire.

GREGORY OF NYSSA, Sermon on the Dead [A.D. 385]

Possibly thy inquiry is satisfied by this my brief reply. But what other considerations move me, to which I think meet to answer, do
thou for a short space attend. In the books of the Maccabees we read of sacrifice offered for the dead.2 Howbeit even if it were no
where at all read in the Old Scriptures, not small is the authority, which in this usage is clear, of the whole Church, namely, that in the
prayers of the priest which are offered to the Lord God at His altar, the Commendation of the dead hath also its place.

AUGUSTINE, On Care To Be Had For The Dead, Chapter 1:3 [A.D. 354-430]

... there must be a cleansing fire before judgement, because of some minor faults that may remain to be purged away. Does not Christ,
the Truth, say that if anyone blasphemes against the Holy Spirit he shall not be forgiven 'either in this world or in the world to come? '
From this statement we learn that some sins can be forgiven in this world and some in the world to come. For if forgiveness of sins is
refused for some particular sin, we conclude logically that it is granted for others (St. Gregory the Great 247).

POPE LEO I THE GREAT, Dialogues Book 4 [A.D. 461]