These quotes are from two sources (here and here)
“Polycarp declared, ‘Eighty and six years have I served Him, and He never did me injury: how then can I blaspheme my King and Saviour?”Polycarp,Martyrdom of Polycarp,9(A.D. 156),in ANF,I:41
“I, therefore, brethren, who have lived sixy-five years in the Lord.” Polycrates,Fragment in Eusebius’ Church History, V:24:7(A.D. 190),in NPNF2,I:242
“He [Jesus] came to save all through himself; all, I say, who through him are reborn in God: infants, and children, and youths, and old men. Therefore he passed through every age, becoming an infant for infants, sanctifying infants; a child for children, sanctifying those who are of that age . . . [so that] he might be the perfect teacher in all things, perfect not only in respect to the setting forth of truth, perfect also in respect to relative age” (Against Heresies 2:22:4 [A.D. 189]).
“Baptize first the children, and if they can speak for themselves let them do so. Otherwise, let their parents or other relatives speak for them” (The Apostolic Tradition 21:16 [A.D. 215]).
“Every soul that is born into flesh is soiled by the filth of wickedness and sin. . . . In the Church, baptism is given for the remission of sins, and, according to the usage of the Church, baptism is given even to infants. If there were nothing in infants which required the remission of sins and nothing in them pertinent to forgiveness, the grace of baptism would seem superfluous” (Homilies on Leviticus 8:3 [A.D. 248]).
“[T]herefore children are also baptized.” Origen,Homily on Luke,XIV(A.D. 233),in JER, 65
“The Church received from the apostles the tradition of giving baptism even to infants. The apostles, to whom were committed the secrets of the divine sacraments, knew there are in everyone innate strains of [original] sin, which must be washed away through water and the Spirit” (Commentaries on Romans 5:9 [A.D. 248]).
Cyprian of Carthage
“As to what pertains to the case of infants: You [Fidus] said that they ought not to be baptized within the second or third day after their birth, that the old law of circumcision must be taken into consideration, and that you did not think that one should be baptized and sanctified within the eighth day after his birth. In our council it seemed to us far otherwise. No one agreed to the course which you thought should be taken. Rather, we all judge that the mercy and grace of God ought to be denied to no man born” (Letters 64:2 [A.D. 253]).
“If, in the case of the worst sinners and those who formerly sinned much against God, when afterwards they believe, the remission of their sins is granted and no one is held back from baptism and grace, how much more, then, should an infant not be held back, who, having but recently been born, has done no sin, except that, born of the flesh according to Adam, he has contracted the contagion of that old death from his first being born. For this very reason does he [an infant] approach more easily to receive the remission of sins: because the sins forgiven him are not his own but those of another” (ibid., 64:5).
Gregory of Nazianzus
“Do you have an infant child? Allow sin no opportunity; rather, let the infant be sanctified from childhood. From his most tender age let him be consecrated by the Spirit. Do you fear the seal [of baptism] because of the weakness of nature? Oh, what a pusillanimous mother and of how little faith!” (Oration on Holy Baptism 40:7 [A.D. 388]).
“‘Well enough,’ some will say, ‘for those who ask for baptism, but what do you have to say about those who are still children, and aware neither of loss nor of grace? Shall we baptize them too?’ Certainly [I respond], if there is any pressing danger. Better that they be sanctified unaware, than that they depart unsealed and uninitiated” (ibid., 40:28).
“You see how many are the benefits of baptism, and some think its heavenly grace consists only in the remission of sins, but we have enumerated ten honors [it bestows]! For this reason we baptize even infants, though they are not defiled by [personal] sins, so that there may be given to them holiness, righteousness, adoption, inheritance, brotherhood with Christ, and that they may be his [Christ’s] members” (Baptismal Catecheses in Augustine, Against Julian 1:6:21 [A.D. 388]).
“What the universal Church holds, not as instituted [invented] by councils but as something always held, is most correctly believed to have been handed down by apostolic authority. Since others respond for children, so that the celebration of the sacrament may be complete for them, it is certainly availing to them for their consecration, because they themselves are not able to respond” (On Baptism, Against the Donatists 4:24:31 [A.D. 400]).
“The custom of Mother Church in baptizing infants is certainly not to be scorned, nor is it to be regarded in any way as superfluous, nor is it to be believed that its tradition is anything except apostolic” (The Literal Interpretation of Genesis 10:23:39 [A.D. 408]).
“Cyprian was not issuing a new decree but was keeping to the most solid belief of the Church in order to correct some who thought that infants ought not be baptized before the eighth day after their birth. . . . He agreed with certain of his fellow bishops that a child is able to be duly baptized as soon as he is born” (Letters 166:8:23 [A.D. 412]).
“By this grace baptized infants too are ingrafted into his [Christ’s] body, infants who certainly are not yet able to imitate anyone. Christ, in whom all are made alive . . . gives also the most hidden grace of his Spirit to believers, grace which he secretly infuses even into infants. . . . It is an excellent thing that the Punic [North African] Christians call baptism salvation and the sacrament of Christ’s Body nothing else than life. Whence does this derive, except from an ancient and, as I suppose, apostolic tradition, by which the churches of Christ hold inherently that without baptism and participation at the table of the Lord it is impossible for any man to attain either to the kingdom of God or to salvation and life eternal? This is the witness of Scripture, too. . . . If anyone wonders why children born of the baptized should themselves be baptized, let him attend briefly to this. . . . The sacrament of baptism is most assuredly the sacrament of regeneration” (Forgiveness and the Just Deserts of Sin, and the Baptism of Infants 1:9:10; 1:24:34; 2:27:43 [A.D. 412]).