Quotes about universal salvation (i.e., everyone will eventually be saved) from throughout Christian History. I have not supplied this page with quotes from Origen yet. He was a universalist. These quotes are from before Origen, and the idea of universal salvation is simply absent from the fathers before Origen.
Anonymous Letter to Diognetus, c. 80-150
God ... who made all things, and assigned them their several positions, proved himself not merely a friend of mankind, but also patient. Yes, he was always of such a character, still is, and will ever be kind and good, free from wrath, true, and the only one who is good. (ch. 8)
You will condemn the deceit and error of the world when you know what it is to live truly in heaven; when you despise what is esteemed to be death here; when you fear what is truly death, which is reserved for those who shall be condemned to the eternal fire. It will afflict to the end those that are committed to it. Then you will admire those who, for righteousness’ sake, endure the fire that is but for a moment, and will consider them happy when you understand that fire. (ch. 10)
Theophilus of Antioch, c. 170
This first quote has been oddly cited in defense of universalism. It simply teaches that even though God drove Adam out of Paradise, his purpose was to restore us. The second quote gives Theophilus' real thoughts about eternity.
And God showed great kindness to man in this, that He did not suffer him to remain in sin for ever; but, as it were, by a kind of banishment, cast him out of Paradise, in order that, having by punishment expiated, within an appointed time, the sin, and having been disciplined, he should afterwards be restored. (To Autolycus, II:26)
But to the unbelieving and despisers, who obey not the truth, but are obedient to unrighteousness, when they shall have been filled with adulteries, fornications, filthiness, covetousness, and unlawful idolatries, there shall be anger and wrath, tribulation and anguish, and at the very end everlasting fire shall possess such men. Since you said, "Show me your God," this is my God, and I counsel you to fear him and to trust him. (To Autolycus, I:14)
Irenaeus, c. A.D. 185
In addition to his blasphemy against God Himself, [Marcion] advanced this also, truly speaking as with the mouth of the devil, and saying all things in direct opposition to the truth,—that Cain, and those like him, and the Sodomites, and the Egyptians, and others like them, and, in fine, all the nations who walked in all sorts of abomination, were saved by the Lord, on His descending into Hades, and on their running unto Him, and that they welcomed Him into their kingdom. But the serpent which was in Marcion declared that Abel, and Enoch, and Noah, and those other righteous men who sprang from the patriarch Abraham, with all the prophets, and those who were pleasing to God, did not partake in salvation. For since these men, he says, knew that their God was constantly tempting them, so now they suspected that He was tempting them, and did not run to Jesus, or believe His announcement: and for this reason he declared that their souls remained in Hades. (Against Heresies, I:27:3)
Clement of Alexandria, c. 190
Clement of Alexandria is often referenced as a teacher who believed in universal salvation. You will have to determine that for yourself based on the following quotes. If I am leaving out anything important from Clement, please let me know.
Look to the threatening! Look to the exhortation! Look to the punishment! Why ... should we any longer change grace into wrath, and not receive the word with open ears and entertain God as a guest in pure spirits? For great is the grace of His promise, "if today we hear His voice." ...
For the today signifies eternity. ...
Rightly, then, to those that have believed and obey, grace will superabound, while with those that have been unbelieving, and err in heart, and have not known the Lord’s ways ... God is incensed, and those he threatens. (Exhortation to the Heathen 9)
Oh, the prodigious folly of being ashamed of the Lord! He offers freedom, you flee into bondage; he bestows salvation, you sink down into destruction; he confers everlasting life, you wait for punishment and prefer the fire which the Lord "has prepared for the devil and his angels." (Exhortation to the Heathen 9)
And you know not that, of all truths, this is the truest, that the good and godly shall obtain the good reward, inasmuch as they held goodness in high esteem. An the other hand, the wicked shall receive appropriate punishment.
For the author of evil, torment has been prepared; and so the prophet Zecharias threatens him: "He that has chosen Jerusalem rebuke you ..." What an infatuated desire, then, for voluntary death is this, rooted in men’s minds! Why do they flee to this fatal brand, with which they shall be burned, when it is within their power to live nobly according to God ... ?" For God bestows life freely; but evil custom, after our departure from this world, brings on the sinner unavailing remorse with punishment. (Exhortation to the Heathen 10)
And, on the other hand, He is in no respect whatever the cause of evil. For all things are arranged with a view to the salvation of the universe by the Lord of the universe, both generally and particularly. It is then the function of the righteousness of salvation to improve everything as far as practicable. For even minor matters are arranged with a view to the salvation of that which is better, and for an abode suitable for people’s character. Now everything that is virtuous changes for the better; having as the proper cause of change the free choice of knowledge, which the soul has in its own power. But necessary corrections, through the goodness of the great overseeing Judge, both by the attendant angels, and by various acts of anticipative judgment, and by the perfect judgment, compel egregious sinners to repent. (Miscellanies, VII:2)