St. Basil the Great
“For prisoners, baptism is ransom, forgiveness of debts, death of sin, regeneration of the soul, a resplendent garment, an unbreakable seal, a chariot to heaven, a protector royal, a gift of adoption” (Sermons on Moral and Practical Subjects: On Baptism 13:5 [ante A.D. 379]).
St. Clement of Alexandria
“When we are baptized we are enlightened. Being enlightened, we are adopted as sons. Adopted as sons, we are made perfect. Made perfect, we become immortal. ‘I say,’ God declares, ‘you are gods and sons all of the Most High’ (Psalm 81:6). This work is variously called grace, illumination, perfection, and washing. It is a washing by which we are cleansed of sins; a gift of grace by which the punishments due our sins are remitted; an illumination by which we behold that holy light of salvation – that is, by which we see God clearly; and we call that perfection which leaves nothing lacking. Indeed, if a man know God, what more does he need? Certainly, it were out of place to call that which is not complete a true gift of God’s grace. Because God is perfect the gifts he bestows are perfect” (The Instructor of Children 1:6, 26:1 [ante A.D. 202]).
We call it, the Gift, the Grace, Baptism, Unction, Illumination, the Clothing of Immortality, the Laver of Regeneration, the Seal, and everything that is honourable (Gregory of Nazianz , On Holy Baptism , Oratio XL)
St. John Chrysostom’s “Baptismal Instructions,” Talking to the newly baptized, he says (3d Instruction):
Let us say again: Blessed be God, who alone does wonderful things, who does all things and transforms them. Before yesterday you were captives, but now you are free and citizens of the Church; lately you lived in the shame of your sins, but now you live in freedom and justice. You are not only free, but also holy; not only holy, but also just; not only just, but also sons; not only sons, but also heirs; not only heirs, but also brothers of Christ; not only brothers of Christ, but also joint heirs; not only joint heirs, but also members; not only members, but also the temple; not only the temple, but also instruments of the Spirit.
Augustine on Baptism Against the Donatists, Book 4 : 1-2
The comparison of the Church with Paradise(1) shows us that men may indeed receive her baptism outside her pale, but that no one outside can either receive or retain the salvation of eternal happiness. For, as the words of Scripture testify, the streams from the fountain of Paradise flowed copiously even beyond its bounds. Record indeed is made of their names; and through what countries they flow, and that they are situated beyond the limits of Paradise, is known to all;(2) and yet in Mesopotamia, and in Egypt, to which countries those rivers extended, there is not found that blessedness of life which is recorded in Paradise. Accordingly, though the waters of Paradise are found beyond its boundaries, yet its happiness is in Paradise alone. So, therefore, the baptism of the Church may exist outside, but the gift of the life of happiness is found alone within the Church, which has been rounded on a rock, which has received the keys of binding and loosing.(3) "She it is alone who holds as her privilege the whole power of her Bridegroom and Lord;"(4) by virtue of which power as bride, she can bring forth sons even of handmaids. And these, if they be not high-minded, shall be called into the lot of the inheritance; but if they be high-minded, they shall remain outside.
All the more, then, because "we are fighting s for the honor and unity" of the Church, let us beware of giving to heretics the credit of whatever we acknowledged among them as belonging to the Church; but let us teach them by argument, that what they possess that is derived from unity is of no efficacy to their salvation, unless they shall return to that same unity. For "the water of the Church is full of faith, and salvation, and holiness"(6) to those who use it rightly. No one, however, can use it well outside the Church. But to those who use it perversely, whether within or without the Church, it is employed to work punishment, and does not conduce to their reward. And so baptism "cannot be corrupted and polluted," though it be handled by the corrupt or by adulterers, just as also "the Church herself is uncorrupt, and pure, and chaste."(7) And so no share in it belongs to the avaricious, or thieves, or usurers,--many of whom, by the testimony of Cyprian himself in many places of his letters, exist not only without, but actually within the Church,--and yet they both are baptized and do baptize, with no change in their hearts.