The same reason Justin Martyr thought that.
“For Christ also said, ‘Except ye be born again, ye shall not enter into the kingdom of heaven.’ Now, that it is impossible for those who have once been born to enter into their mothers’ wombs, is manifest to all. And how those who have sinned and repent shall escape their sins, is declared by Esaias the prophet, as I wrote above; he thus speaks: ‘Wash you, make you clean; put away the evil of your doings from your souls; learn to do well…And though your sins be as scarlet, I will make them white like wool; and though they be as crimson, I will make them white as snow…And for this [rite] we have learned from the apostles this reason. Since at our birth we were born without our own knowledge or choice, by our parents coming together, and were brought up in bad habits and wicked training; in order that we may not remain the children of necessity and of ignorance, but may become the children of choice and knowledge, and may obtain in the water the remission of sins formerly committed, there is pronounced over him who chooses to be born again, and has repented of his sins, the name of God the Father and Lord of the universe; he who leads to the laver the person that is to be washed calling him by this name alone…And this washing is called illumination, because they who learn these things are illuminated in their understandings. And in the name of Jesus Christ, who was crucified under Pontius Pilate, and in the name of the Holy Ghost, who through the prophets foretold all things about Jesus, he who is illuminated is washed.” Justin Martyr, First Apology, 61 (A.D. 110-165).
The same reason Irenaeus and Tertullian thought that.
” ‘And dipped himself,’ says [the Scripture], ‘seven times in Jordan.’ It was not for nothing that Naaman of old, when suffering from leprosy, was purified upon his being baptized, but it served as an indication to us. For as we are lepers in sin, we are made clean, by means of the sacred water and the invocation of the Lord, from our old transgressions; being spiritually regenerated as new-born babes, even as the Lord has declared: ‘Except a man be born again through water and the Spirit, he shall not enter into the kingdom of heaven.'” Irenaeus, Fragment, 34 (A.D. 190).
“When, however, the prescript is laid down that ‘without baptism, salvation is attainable by none” (chiefly on the ground of that declaration of the Lord, who says, “Unless one be born of water, he hath not life.'” Tertullian, On Baptism, 12:1 (A.D. 203).
The same reason Origen, Cyprian and the entire council of Carthage thought that.
“The Church received from the Apostles the tradition of giving Baptism even to infants. For the Apostles, to whom were committed the secrets of divine mysteries, knew that there is in everyone the innate stains of sins, which must be washed away through water and the Spirit.” Origen, Commentary on Romans, 5:9 (A.D. 244).
“[W]hen they come to us and to the Church which is one, ought to be baptized, for the reason that it is a small matter to ‘lay hands on them that they may receive the Holy Ghost,’ unless they receive also the baptism of the Church. For then finally can they be fully sanctified, and be the sons of God, if they be born of each sacrament; since it is written, ‘Except a man be born again of water, and of the Spirit, he cannot enter into the kingdom of God.’…[O]nly baptism of the holy Church, by divine regeneration, for the kingdom of God, may be born of both sacraments, because it is written, ‘Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.'” Cyprian, To Stephen, 71:72 (A.D. 253).
“And in the Gospel our Lord Jesus Christ spoke with His divine voice, saying, “Except a man be born again of water and the Spirit, he cannot enter the kingdom of God.” This is the Spirit which from the beginning was borne over the waters; for neither can the Spirit operate without the water, nor the water without the Spirit…Unless therefore they receive saving baptism in the Catholic Church, which is one, they cannot be saved, but will be condemned with the carnal in the judgment of the Lord Christ.” Council of Carthage VII (A.D. 258).
How many kindreds of the same thought do I find among the ancient Fathers.
What were they referring to for that thought.