Baptisms described, AD 100—400

Below are some examples of the understanding of baptism among early Christian writers. I do not advocate all of their theology, some with which I would widely differ. But their incidental and deliberate statements on baptism suggest immersion was the standard and predominant mode among them -- as well as confirming the early ties of the theology of baptism with the death, burial and resurrection of Jesus Christ. The quotes are arranged in roughly alphabetical order. Links are provided for those who would like to research the source material.

Baptism is by immersion, but by pouring if the water is insufficient for immersion *
Chapter 7. Concerning Baptism. And concerning baptism, baptize this way: Having first said all these things, baptize into the name of the Father, and of the Son, and of the Holy Spirit, in living water. But if you have no living water, baptize into other water; and if you cannot do so in cold water, do so in warm. But if you have neither, pour out water three times upon the head into the name of Father and Son and Holy Spirit. But before the baptism let the baptizer fast, and the baptized, and whoever else can; but you shall order the baptized to fast one or two days before. – Didache (parts of original possibly before AD 100, with other material added later; it was rediscovered in 1873)

Baptism is by immersion, but by pouring if the water is insufficient for immersion
VII 1. Περὶ δὲ τοῦ βαπτίσματος, οὕτω βαπτίσατε· ταῦτα πάντα πρειπόντες, βαπτίσατε εἰς τὸ ὄνομα τοῦ πατρὸς καὶ τοῦ υἱοῦ καὶ τοῦ ἁγίου πνεύματος ἐν ὕδατι ζῶντι. 2. ἐὰν δὲ μὴ ἔχῃς ὕδωρ ζῶν, εἰς ἄλλο ὕδωρ βάπτισον· εἰ δ’ οὐ δύνασαι ἐν ψυχρῷ, ἐν θερμῷ. 3. ἐὰν δὲ ἀμφότερα μὴ ἔχῃς, ἔκχεον εἰς τὴν κεφαλὴν τρὶς ὕδωρ εἰς ὄνομα πατρὸς καὶ υἱοῦ καὶ ἁγίου πνεύματος. 4. πρὸ δὲ τοῦ βαπτίσμος προνηστευσάτω ὁ βαπτίζων καὶ ὁ βαπτιζόμενος καὶ εἴ τινες ἄλλοι δύναται· κελεύεις δὲ νηστεῦσαι τὸν βαπτιζόμενον πρὸ μιᾶς ἢ δύο. Didache (in Greek)

Baptism, descending and coming up
This means, that we indeed descend into the water full of sins and defilement, but come up, bearing fruit in our heart, having the fear [of God] and trust in Jesus in our spirit. -- The Epistle of Barnabas (ca. 70-100), Chapter 11, translated by Alexander Roberts and James Donaldson, from Ante-Nicene Fathers, Vol. 1

Baptism, descending into the water
And I said, "I heard, sir, some teachers maintain that there is no other repentance than that which takes place, when we descended into the water and received remission of our former sins." He said to me, "That was sound doctrine which you heard; for that is really the case..." -- The Shepherd of Hermas (1st or 2nd century)

Baptism, descending in death and rising in life
The seal, then, is the water: they descend into the water dead, and they arise alive. And to them, accordingly, was this seal preached, and they made use of it that they might enter into the kingdom of God." "Why, sir," I asked, "did the forty stones also ascend with them out of the pit, having already received the seal?" "Because," he said, "these apostles and teachers who preached the name of the Son of God, after falling asleep in the power and faith of the Son of God, preached it not only to those who were asleep, but themselves also gave them the seal of the preaching. Accordingly they descended with them into the water, and again ascended. -- The Shepherd of Hermas (1st or 2nd century)

Baptism, a washing with water
Chapter 61. I will also relate the manner in which we dedicated ourselves to God when we had been made new through Christ; lest, if we omit this, we seem to be unfair in the explanation we are making. As many as are persuaded and believe that what we teach and say is true, and undertake to be able to live accordingly, are instructed to pray and to entreat God with fasting, for the remission of their sins that are past, we praying and fasting with them. Then they are brought by us where there is water, and are regenerated in the same manner in which we were ourselves regenerated. For, in the name of God, the Father and Lord of the universe, and of our Saviour Jesus Christ, and of the Holy Spirit, they then receive the washing with water. -- Justin Martyr (ca. 100-165), The First Apology

Baptism, bringing persons to water as opposed to pouring on oil and water
21.4 But there are some of them who assert that it is superfluous to bring persons to the water, but mixing oil and water together, they place this mixture on the heads of those who are to be initiated, with the use of some such expressions as we have already mentioned. -- Irenaeus of Lyons (130-200), Book I

Baptism, immersion three times
Luke 23:46 After His resurrection He promises in a pledge to His disciples that He will send them the promise of His Father; Luke 24:49 and lastly, He commands them to baptize into the Father and the Son and the Holy Ghost, not into a unipersonal God. And indeed it is not once only, but three times, that we are immersed into the Three Persons, at each several mention of Their names. -- Tertullian (ca. 160-230), Against Praxeas, Chapter 26, translated by Peter Holmes, from Ante-Nicene Fathers, Vol. 3

Baptism – thrice immersed
To deal with this matter briefly, I shall begin with baptism. When we are going to enter the water, but a little before, in the presence of the congregation and under the hand of the president, we solemnly profess that we disown the devil, and his pomp, and his angels. Hereupon we are thrice immersed, making a somewhat ampler pledge than the Lord has appointed in the Gospel. – Tertullian (ca. 160-230, De Corona, Chapter 3, translated by S. Thelwall, from Ante-Nicene Fathers, Vol. 3

Baptism, plunged in water
Thus, too, in our case, the unction runs carnally, (i.e. on the body,) but profits spiritually; in the same way as the act of baptism itself too is carnal, in that we are plunged in water, but the effect spiritual, in that we are freed from sins. – Tertullian (ca. 160-230, On Baptism, translated by S. Thelwall, from Ante-Nicene Fathers, Vol. 3

Baptism, a bath or laver of regeneration
(trans. 1) The ropes that stretch around her [the ship of the church] are the love of Christ, which binds the church. The net that she bears with her is the bath of the regeneration that renews the believing, from which too are these glories. 
(trans. 2) and the ropes that stretch around her are the love of Christ, which binds the Church; and the net which she bears with her is the laver of the regeneration which renews the believing, whence too are these glories. -- Hippolytus (170-236), Translation 1 as found in Worshipping with the Church Fathers (Christopher A. Hall, Downers Grove, IL: IVP Academic, 2009 page 44) and Translation 2 as found in On Christ and Antichrist

Baptism includes descending in the water
16. ...And some of them try to argue that they only administer a sound and perfect, not as we, a mutilated and curtailed baptism, which they are in such wise said to designate, that immediately they have descended into the water, fire at once appears upon the water. -- A Treatise on Re-Baptism (ca. 255)

Baptism different from sprinkling or affusion, though allowing the latter for the infirm
12. You have asked also, dearest son, what I thought of those who obtain God's grace in sickness and weakness, whether they are to be accounted legitimate Christians, for that they are not to be washed, but sprinkled, with the saving water. In this point, my diffidence and modesty prejudges none, so as to prevent any from feeling what he thinks right, and from doing what he feels to be right...13...And therefore, as far as it is allowed me by faith to conceive and to think, this is my opinion, that any one should be esteemed a legitimate Christian, who by the law and right of faith shall have obtained the grace of God in the Church. Or if any one think that those have gained nothing by having only been sprinkled with the saving water, but that they are still empty and void, let them not be deceived, so as if they escape the evil of their sickness, and get well, they should seek to be baptized. But if they cannot be baptized who have already been sanctified by ecclesiastical baptism, why are they offended in respect of their faith and the mercy of the Lord? -- Cyprian of Carthage (d. 258), Epistle 75, To Magnus

Baptism a sinking down and rising up, signifying burial and resurrection
In these benefits you were baptized, O newly-enlightened one. The initiation in grace, O newly-enlightened one, has become to you a guarantee of resurrection; you have baptism as a pledge of life in heaven. In the sinking down you imitated the burial of the Master; but you rose up from there, beholding beforehand the works of the resurrection. -- Discourse on the Holy Passover (attributed to Athansius, ca. 296–373) as quoted in Baptism in the Early Church: History, Theology, and Liturgy in the First Five Centuries, by Everett Ferguson (Grand Rapids, MI: William B. Eerdmans, 2009, pp. 492-493)

Baptism a dipping in water
3.XVI. You therefore, O bishop, according to that type, shall anoint the head of those that are to be baptized, whether they be men or women, with the holy oil, for a type of the spiritual baptism. After that, either you, O bishop, or a presbyter that is under you, shall in the solemn form name over them the Father, and Son, and Holy Spirit, and shall dip them in the water; and let a deacon receive the man, and a deaconess the woman, that so the conferring of this inviolable seal may take place with a becoming decency. And after that, let the bishop anoint those that are baptized with ointment. Apostolic Constitutions, Book III (ca. 375)

Baptism by three immersions, in the name of the Father, and of the Son, and of the Holy Ghost
8.50. If any bishop or presbyter does not perform the three immersions of the one admission, but one immersion, which is given into the death of Christ, let him be deprived; for the Lord did not say, Baptize into my death, but, Go and make disciples of all nations, baptizing them into the name of the Father, and of the Son, and of the Holy Ghost. Therefore, O bishops, baptize thrice into one Father, and Son, and Holy Ghost, according to the will of Christ, and our constitution by the Spirit. -- Apostolic Constitutions, Book VIII (ca. 375)

Baptism in a pool, consisting of descending into and ascending from water
20.4 After these things, you were led to the holy pool of Divine Baptism, as Christ was carried from the Cross to the Sepulchre which is before our eyes. And each of you was asked, whether he believed in the name of the Father, and of the Son, and of the Holy Ghost, and you made that saving confession, and descended three times into the water, and ascended again; here also hinting by a symbol at the three days burial of Christ. -- Cyril of Jerusalem (ca. 313–386 AD), Catechetical Lecture 20

Baptism a going down and coming up
3.12 For you go down into the water, bearing your sins, but the invocation of grace , having sealed your soul, suffers you not afterwards to be swallowed up by the terrible dragon. Having gone down dead in sins, you come up quickened in righteousness. For if you have been united with the likeness of the Saviour's death Romans 6:5, you shall also be deemed worthy of His Resurrection. For as Jesus took upon Him the sins of the world, and died, that by putting sin to death He might rise again in righteousness; so thou by going down into the water, and being in a manner buried in the waters, as He was in the rock, art raised again walking in newness of life. -- Cyril of Jerusalem (ca. 313–386 AD), Catechetical Lecture 3

Baptism consists of three immersions
15.35 This then is what it is to be born again of water and of the Spirit, the being made dead being effected in the water, while our life is wrought in us through the Spirit. In three immersions, then, and with three invocations, the great mystery of baptism is performed, to the end that the type of death may be fully figured, and that by the tradition of the divine knowledge the baptized may have their souls enlightened. -- Basil the Great (ca. 329-379), De Spiritu Sancto

Baptism, burial and resurrection, descending and rising 
We call it the Gift, because it is given to us in return for nothing on our part; Grace, because it is conferred even on debtors; Baptism, because sin is buried with it in the water...Let us then be buried with Christ by Baptism, that we may also rise with Him; let us descend with Him, that we may also be exalted with Him; let us ascend with Him, that we may also be glorified together. -- Gregory Nazianzen (ca. 329–390), Oration 40, on holy Baptism

Baptism, a dipping and burial 
11. The water, then, is that in which the flesh is dipped, that all carnal sin may be washed away. All wickedness is there buried... 21. So that Syrian dipped himself seven times under the law, but you were baptized in the Name of the Trinity, you confessed the Father. Call to mind what you did: you confessed the Son, you confessed the Holy Spirit. Mark well the order of things in this faith: you died to the world, and rose again to God. And as though buried to the world in that element, being dead to sin, you rose again to eternal life. Believe, therefore, that these waters are not void of power. Ambrose (340-397), On the Mysteries

Baptism immersion 
How and in what manner? By the water. For the being baptized and immersed and then emerging, is a symbol of the descent into Hades and return thence. Wherefore also Paul calls baptism a burial, saying, Therefore we are buried with Him by baptism into death. -- John Chrysostom (ca. 349–407) Homily 40 on First Corinthians

The above examples are not considered authoritative (only the Holy Scriptures are), but are presumed to be historically accurate and representative of the faith and practice of the writer. There seems to be a fairly consistent thread of immersion that runs through the writings of the early "Church Fathers".

Archaelogy
"The predominant number of baptismal fonts permitted immersion, and many were so large as to defy any reason for their existence other than immersion." (Baptism in the Early Church, Everett Ferguson p. 883)

* It is generally conceded that parts of the Didache have an origin as early as AD 100 (or even earlier), with later editing. This work was discovered in 1873 in the Constantinople Manuscripts by Greek Orthodox Archbishop Philotheus Bryennios. It was published 1883. It is dated as copied in 1056. In his notes on translation in 1937, J. Louis Guthrie stated that he believed that the instruction on baptism by pouring was a late addition, "for it shows the insertion of a different scribe." He says, "The direction concerning pouring is the worst possible Greek. It is so bad, it does not make sense. He gives the literal translation as "But, if you may not have both, pour out into the head three water into a name Father and Son and Holy Spirit." (The Didache of the Twelve Apostles, J. Louis Guthrie, 1938, pp. 10, 19) Schaff appears to disagree with this assessment (that the pouring reference is late). See The Oldest Church Manual Called The Teaching of the Twelve Apostles: Didachē, p. 35.