I'm asking if the baby receives some sanctification that it did not have prior to the baptism in Orthodox theology.
All sacraments bring an experience of grace - God's energies - to us, so yes, absolutely.
I thought this article addressed the questions well, though it is addressed to protestant objections:
Infant Baptism: What the Church Believes | Antiochian Orthodox Christian Archdiocese
Is infant baptism biblical?
Yes, it is. While there is no description of an individual infant being baptized, the Bible describes five separate household baptisms:
The Household of Cornelius, Acts 11:1314: Send men to Joppa, and call for Simon whose surname is Peter, who will tell you words by which you and all your household will be saved.
The Household of Lydia, Acts 16:15: And when she and her household were baptized, she begged us, saying, If you have judged me to be faithful to the Lord, come to my house and stay. So she persuaded us.
The Philippian Jailors Household, Acts 16:33: And he took them the same hour of the night and washed their stripes. And immediately he and all his family were baptized.
The Household of Crispus, Acts 18:8: Then Crispus, the ruler of the synagogue, believed on the Lord with all his household. And many of the Corinthians, hearing, believed and were baptized.
The Household of Stephanas, 1 Corinthians 1:16: Yes, I also baptized the household of Stephanas.
Some have argued that while the Bible may say household or family this does not have to include children. Maybe those households did not include children. While this may be the case, it is hard to imagine that at least one of these households did not include children. And given the fact that we have five explicit references to a whole household being baptized, we have to assume that many, many more such households were baptized. Surely some of them included children.
The word household for any Israelite of the day included everybody in the household, children included. We must remember that a household always included children throughout the Scriptures. Every time God established or spoke about His covenant with the House of Israel, it included the whole of Israel: men, women, and children. Noahs whole household was taken into the ark with him (Genesis 7:1); Abraham had his whole household circumcised (Genesis 17:23), and specifically his son Isaac when he was eight days old (Genesis 21:4); the whole household of every family was taken out of Egypt, and Gods institution of the Passover specifically included the children (Exodus 12:2428). If the Apostles had taught that children were to be excluded from full inclusion in the covenant, such an innovation would not have fit the prophetic covenants which preceded the fulfilled covenant enacted through Christ.
The pattern of the Old Testament covenants formed the framework for the apostolic understanding of the true covenant of Christ, and those covenants included children. They were covenants which were made with a nation, in which every household participated. This is what is expressed in the household baptisms of the New Testament. Even when an individual was baptized, this baptism placed him in a larger body. Individual adult baptisms occurred, but there were no individual covenants.
The Bible teaches us that under the Old Covenant, every male child was circumcised on the eighth day after birth. With his circumcision, the child became a full and complete member of the covenant and could eat of the Passover sacrifice. Baptism in Christ absorbed and fulfilled this rite, as it absorbed all initiation and cleansing rites of the day. Circumcision, we know from the first council in Jerusalem (Acts 15:5; Acts 21:21), was no longer necessary for the Gentile convert or his children. Nowhere in the Bible is it hinted that while absorbing the rite of circumcision, baptism would suddenly and without precedent exclude children. Jesus did not have a problem with children gaining full inclusion to the covenant: He Himself was circumcised as an infant (Luke 2:21), like John the Forerunner (Luke 1:59).
Here we need to introduce a statement by Jesus Himself on the subject of children and faith. In Luke 18, some children are brought to Him to receive a blessing. His disciples try to interfere. But Jesus immediately rebukes them, saying, Let the little children come to Me, and do not forbid them; for of such is the kingdom of God (Luke 18:16). A sentimental reading of this passage tells us that Jesus loves children, and that we should not stop them from trying to ask questions about Him or wanting to pray to Him, or tell them that they are too young to get to know Him. While this is true, no one the Lord is talking to thought differently. These were people, we have to remember, who circumcised their children, included them in the Passover rituals and taught them from a young age about God, Israel and the Prophetic writings. The Jews were fanatical, by our modern standards, in their desire to raise their children in the faith. This is not a Hallmark moment in the Gospels.
Jesus is in fact including children in His Kingdom. And His inclusion of children in the Kingdom includes them in the covenant He establishes in His Name. There is no partial involvement in the Kingdom of Heaven, just as there is no partial inclusion in the covenant. We are either members or not. Jesus is saying that children are in, and there is to be no argument about it. There is absolutely no room here to make an argument that children must wait until some magical age before they too can be included with full rights into the Church and at the altar table.
Jesus was once an infant Himself. And Jesus was never separate from God, even in His mothers womb. The heretical Nestorians claimed that Jesus divinity only descended upon Him at baptism. But the Orthodox Church has always declared that He united God and man from the moment of His conception, and the Orthodox believe that His Kingdom belongs to children. Not only because the covenant is with the whole household; not only because a distinction of age was never introduced into the practice of baptism; not only because such a distinction would not have matched the Old Testament covenants which served as the prophetic model for the New Covenant; but because Christ Himself became incarnate as an infant child. In Him all ages, like all humanity, are sewn into the perfect union expressed in the eucharistic supper of the New Israel, which we join only through baptism. Christ makes both childhood and adulthood fully capable of expressing and participating in the Kingdom of Heaven.
But children dont understand the faith!
The assumption behind this objection to infant baptism, one which did not exist in the early Church or in the centuries which followed, is that faith is a product of reason. That to truly believe, our minds must be capable of understanding why we believe, or at least able to provide intellectual consent. For the adult convert to the Orthodox Church, intellectual consent is crucial. Baptism is not magic. It is a voluntary act of submission to God, a consent to live in relationship with God within the covenant He has established through His Son with a larger body of baptized believers, the Church. But at the same time, faith falls flat if it does not go beyond individual reason. It falls flat because it is so individualized, exclusive, and self-centered. Tertullian said famously that one Christian is no Christian. It is true that our faith must be personal, that we must have a personal relationship with God. But our faith must not be limited to that personal relationship alone. Our relationship with God is valid only if it is realized in communion with the whole Church.
Ive spoken of the Church as family, and I want to return to that image. Children can break fellowship with the family if they consider themselves outside the familys fate. They are family members only in so much as they live as part of the family, accepting all the responsibilities and self-sacrifice that such family status demands. I dont have to explain this to my children. They understand from birth that they belong to a larger group, and belong in the most intimate way. They know who their father and mother are and where to go for help and for security. The concept of family is beyond them, but the reality of family life is not. In other words, children have a sense of belonging a dozen years or more before they understand what this belonging means.
The earthly family is an image of the heavenly family, the family of the Kingdom of God. Children born to a Christian family are born again into the heavenly family through baptism. A child baptized in the Orthodox Church belongs to a spiritual family. This family bridges both heaven and earth, stretches backward and forward in time and includes both saints and angels. Children belong to this family exactly as each of my daughters belongs to my family. They know in a profound way that they belong long before they have some kind of cerebral understanding of that belonging.
Our modern world so exults reason and cerebralism that young children are sometimes treated as not fully human, or are at least treated less seriously than adults because they cant think like we do. The truth is that a child is a full human being. A child of any age is capable of expressing and participating in the glory of God. Christ Himself sanctified every age as God-bearing, since He was as much the perfect Word of God as an infant as when He was a grown man. We must remember that children are not second-class persons. Their baptisms are as significant to them and to God as adult baptisms. Even if they do not cognitively understand what that baptism means, they are certainly capable of intuitively understanding it.
What if a child leaves or rejects Christ later in life?
This is a real concern, but not a reason to keep children from full membership in the New Covenant by denying them baptism and communion. We should rather accept them as the Lord commanded us to do, because raising them up in the life in Christ will give them a much better chance of carrying this life beyond our parental guardianship. If someone has no intention of raising a child in Christif they have no intention of attending church, praying as a family in the home, teaching the Bible, encouraging questions about the faith, and giving their children every opportunity to experience the life of the Churchthen they should in no way bring their child to be baptized.
When we decide to baptize a child we make the most solemn of promises to God. We are promising to do everything in our power to bring that child to Christ, and this is a promise that we can only make if we are doing everything we can to draw near to Him ourselves. Children take seriously what we take seriously. If they grow up in a home in which conversations about Christ, prayer, and reading from the Bible and the lives of the saints are part of normal daily life, they will feed off this as much as the food we put on their plates at the dinner table. Children are deeply impressed by candlelight and incense, by flowers at Pascha, by late-night processions during Holy Week, by palm leaves on Palm Sunday, by icons, by lake blessings at Theophany, and by vestments and altar service. All of this fascinates them and draws them into Christ. As a priest, I see just how real the life of faith is to children when they approach the chalice to receive communion. It is in their eyes, and I am humbled. When they see that we are excited and involved, they will become excited and involved. Raising a child in Christ is simple. Just be a child yourself in Christ. Take it seriously. Children take faith very seriously, and we should either honor that faith ourselves or we shouldnt baptize them.
But what if they do leave Christ? What if we do all that we can do and they still walk away? Wouldnt it then have been better not to baptize them? Of course not! Would a responsible parent ever dream of keeping their child outside full family membership until they were sure that the child wants to be in the family? Peter Leithart, a Presbyterian and father of ten children himself, makes an excellent point in his book Against Christianity: Romans normally excluded children from the dinner table until the age of fifteen or sixteen, at which age boys received the toga virilis that marked their entrance to manhood. Family dinner as we know it was a Christian invention, not some natural form of family life. The family dinner is a reflection of the eucharistic meal, the meal that welcomed all members of Christ to the table. Opposition to communion of children is pagan and seeks to reverse the revolutionary table fellowship established by the Church. It is an attempt to return to Egypt.
The family that eats together should receive communion together, the one an image of the other. A child raised in the fullness of the faith has the greatest of foundations. Every human being is free to do Gods will or not. He wants us to choose to do His will. But even when He knows that we wont, He still does not deny us food, clothing, or shelter. He does not deny us love, joy, long life, and children of our own. Will we be so afraid of what our children might do that we deny them the one thing everyone needscommunion in the Church and full membership in the life-giving covenant of Christ? Where is our faith? Where is our resolve? Where is our love for God and for our children? To whom is Christ speaking now, when He says, Let the little children come to Me, and do not forbid them?
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