It was the same when the Old Covenant circumcision was introduced

Just like when God introduced the New Testament, it was the same when God made a covenant with Abraham.

1)      Abraham believed and was circumcised after believing.

2)       Believing God’s word Abraham circumcised his newborn son Isaac who had no say in the matter, at 8 days old based on his faith in God. This continued among his predecessors and later among the Jews and is to this day likewise. Those converting to the faith is circumcised as and when becoming a believer and their offspring at 8 days old. And the Bible says,

Ge:17:23: And Abraham took Ishmael his son, and all that were born in his house, and all that were bought with his money, every male among the men of Abraham's house; and circumcised the flesh of their foreskin in the selfsame day, as God had said unto him. Ge:17:24: And Abraham was ninety years old and nine, when he was circumcised in the flesh of his foreskin.

Ge:21:3: And Abraham called the name of his son that was born unto him, whom Sarah bare to him, Isaac.Ge:21:4: And Abraham circumcised his son Isaac being eight days old, as God had commanded him. Ge:21:5: And Abraham was an hundred years old, when his son Isaac was born unto him. Ge:17:24: And Abraham was ninety years old and nine, when he was circumcised in the flesh of his foreskin.

Ac:7:8: And he gave him the covenant of circumcision: and so Abraham begat Isaac, and circumcised him the eighth day; and Isaac begat Jacob; and Jacob begat the twelve patriarchs.

And the New Testament repeats,

Ro:9:9: For this is the word of promise, At this time will I come, and Sara shall have a son. Ro:9:10: And not only this; but when Rebecca also had conceived by one, even by our father Isaac; Ro:9:11: (For the children being not yet born, neither having done any good or evil, that the purpose of God according to election might stand, not of works, but of him that calleth;)

Ga:4:28: Now we, brethren, as Isaac was, are the children of promise.

Heb:11:18: Of whom it was said, That in Isaac shall thy seed be called

Heb:11:9: By faith he sojourned in the land of promise, as in a strange country, dwelling in tabernacles with Isaac and Jacob, the heirs with him of the same promise:

Isaac is part of the promise through inheritance from birth and thus children of the New Testament are heirs from birth.

Likewise, when the New Covenant was introduced, the ones converting to the faith received the new circumcision of the Spirit which is Baptism, while their newborns are baptized as infants.

We see in the Old Covenant that God commanded Abraham to circumcise himself and all the male children and male servants based on his belief in God. He did likewise and circumcised himself and all the male servants and children. He later circumcised his newborn son Isaac who had no say in the matter, at 8 days old based on Abraham his father’s faith in God. The children made no choice in the matter. God even says that those who are uncircumcised have broken my covenant. Children who have not been circumcised are thus guilty, according to God’s own words. Children come into the Covenant established by God through the family.

We see children in their relation to God necessarily depending upon their parents believing for them. In Ex 4:24f, Moses is on the way back to Egypt and God seeks to kill Moses because Moses neglected to circumcise his son. If circumcision gave spiritual benefits (Gen. 17:14, the part of being within the covenant), how much more would baptism?

Through Physical circumcision one becomes part of  God’s covenant, part of God’s people, Abraham’s children, etc. Likewise in Baptism which is the circumcision by the Holy Spirit, one becomes part of the New covenant by the blood of Jesus, and sons of God, Abraham’s children, etc.

All of Israel was told to sprinkle the blood of the lamb (which prefigured Christ) on the doors of the houses (Exodus 12:13). There was an issue of the firstborn of the land of Egypt and Israel. Those who were in Israel were commanded to sprinkle this blood on their doorposts so God would not destroy their firstborn. The anti-infant baptism mentality might have said “Well, let the children believe for themselves, since they must choose for themselves to sprinkle the lamb’s blood.” Instead, all of Israel, realizing that God works through the covenant, sprinkled the lamb’s blood on the doorpost to save their children. The Egyptians, similar to those against infant baptism, did not sprinkle blood on their doorpost, and all of their firstborn died (Ex. 12:24-28). Neither the firstborn of Israel or Egypt showed any faith. However, the difference was, that those of faith believed for their children while the Egyptians did not believe for their children. If the anti-infant baptism mentality was around, Israel would have ended up with dead babies, just as the Egyptians. Who in the New Covenant should we imitate? The mentality that would have produced dead babies, or the parents who believed for their children and put them in the Covenant of the family of God , and thus saved their children?

We see later in Joshua that God punished the nation of Israel, and those with Joshua because they had not circumcised their children (Joshua 5:2-7.) It was not until all the children were circumcised did God remove the reproach of Egypt from them (Josh. 5:8-9).

We thus see that God puts his children into the Old Covenant through the faith of their parents and grace. Are we to assume that even though in the Old Covenant that children are included in it by their parents faith for them and obedience for them by having them circumcised, that the children are not to be brought into the new covenant? Hardly!!! After all, the grace of the New Covenant far exceeds that of the Old Covenant. Romans 5:15 says,
“But the free gift is not like the trespass. For if many died through one man's trespass, much more have the grace of God and the free gift in the grace of that one man Jesus Christ abounded for many."

It is foretold of what kind the Kingdom of God is to be. Infants and those who convert and become as infants (Mt 19:14). And as in John 3:3-5 What is born of flesh is flesh and what is born of the Spirit is Spirit. So what is born of flesh alone whether it be infants or the grown up who converts as children, has to be born of the Spirit for entry into the Kingdom

Just like because of the faith of Abraham, his son Isaac received the promise even before being born, the faith of a believer plays a part in the salvation of  their offspring. The promise given to Christians is the same promise made to Abraham for which his part was to circumcise all male in the family including infants for which he circumcised his son Isaac when Isaac was only 8 days old. And the Bible says that, it is through Isaac that we become heirs to the promise.

In Jesus’ teaching, we see that spiritual blessing and forgiveness can be given through the faith of others? In Matthew 9:2-6, we see:

2 And behold, they brought to him a paralytic, lying on his bed; and when Jesus saw their faith he said to the paralytic, "Take heart, my son; your sins are forgiven."

Notice it was not the paralytic who chose for himself to accept Jesus words. It was the faith of his friends, which provided not only his physical restoration, but most importantly the forgiveness of his sins!!

M't:15:22-28: And, behold, a woman of Canaan came out of the same coasts, and cried unto him, saying, Have mercy on me, O Lord, thou Son of David; my daughter is grievously vexed with a devil. But he answered her not a word. And his disciples came and besought him, saying, Send her away; for she crieth after us. But he answered and said, I am not sent but unto the lost sheep of the house of Israel. Then came she and worshipped him, saying, Lord, help me.

But he answered and said, It is not meet to take the children's bread, and to cast it to dogs. And she said, Truth, Lord: yet the dogs eat of the crumbs which fall from their masters' table. Then Jesus answered and said unto her, O woman, great is thy faith: be it unto thee even as thou wilt. And her daughter was made whole from that very hour.

M'r:9:17 to 29: And one of the multitude answered and said, Master, I have brought unto thee my son, which hath a dumb spirit; And he asked his father, How long is it ago since this came unto him? And he said, Of a child. And ofttimes it hath cast him into the fire, and into the waters, to destroy him: but if thou canst do any thing, have compassion on us, and help us. Jesus said unto him, If thou canst believe, all things are possible to him that believeth. And straightway the father of the child cried out, and said with tears, Lord, I believe; help thou mine unbelief. When Jesus saw that the people came running together, he rebuked the foul spirit, saying unto him, Thou dumb and deaf spirit, I charge thee, come out of him, and enter no more into him. And the spirit cried, and rent him sore, and came out of him: and he was as one dead; insomuch that many said, He is dead.  But Jesus took him by the hand, and lifted him up; and he arose. M'r:9:29: And he said unto them, This kind can come forth by nothing, but by prayer and fasting.

In Mark 5:22-23 and 40-42, Jairus asks Jesus to save his daughter from death, and in Mark 9:17-27, a father asks Jesus to expel a demon from his son.  Jesus doesn’t turn them away and say, "I have only come to save those who are old enough to make a mature commitment and to accept Me as their personal Lord and Savior."   No.  Jesus responds with power to save them, not because of the children’s faith, but because of their parents’ faith.

We see in Mark 5:23 to 42, a Father acting on behalf of her dying daughter, saying:

My little daughter lieth at the point of death: I pray thee, come and lay thy hands on her, that she may be healed; and she shall live. M'r:5:36: As soon as Jesus heard the word that was spoken, he saith unto the ruler of the synagogue, Be not afraid, only believe. M'r:5:42: And straightway the damsel arose, and walked; for she was of the age of twelve years. And they were astonished with a great astonishment.

Well, this daughter should have believed for herself to receive life!! Nobody could believe for her”, Jesus responding to the faith of her Father. In fact she was now dead. However, Jesus, acting on the faith of her Father, restored her to life.

Likewise parents who believe can based on their belief act to give life in the Spirit to their children.

Infant Baptism strongly conveys the important truth that our salvation is completely dependent on God and His free gift of unearned Grace.  We must cooperate with his grace and receive it, but we even need the help of His grace to do that.  We don’t earn our salvation through a work, that is totally our own, of offering up our faith.    Titus 3:5, "Not because of any righteous deeds we had done, but because of His mercy He saved us through the bath of rebirth and renewal by the Holy Spirit."  Salvation  is a free gift from God.  Even our faith is only made possible by the help of God’s grace.  Infant Baptism conveys this truth that our salvation is truly a free gift from God.   This supernatural faith is not something that comes from within ourselves, but rather, it is God’s gift to us, rather than our gift to God.  John 6:44   "No one can come to me unless the Father who sent me, draw him..."
 

So, it is not that we make an act of saving faith, and then only after which we receive God’s grace, but rather, the grace of God must first come into ourselves so that we are capable of having a supernatural, saving faith.

In not even one instance does He say ‘let them come back after reaching the age of reason’, but cures them at the prayers or mediation of the parents or guardians. Then how much more happy would He be to give His Holy Spirit to little children on the mediation and faith of their parents. He said fathers of this world no matter how evil they are, they give good gifts to their children and how much more happy is the Father in heaven to give the Holy Spirit to His children . Lu:11:13: If ye then, being evil, know how to give good gifts unto your children: how much more shall your heavenly Father give the Holy Spirit to them that ask him?

Then how is it wrong when the fathers of this world give their children the ‘first’ spiritual gift ; the Holy Spirit to their children, and how much more eagerly will the Father in heaven give the Holy Spirit to the children if their parents ‘ask’ for it. Jesus showed it to be that way.

Christ Reigns!!