Would say that under the Old covenant, God was and did remit and hold not their sins against them due to the coming Messiah, just as he does that towards infants who die today, but would say that the born again experience for all believers, the permanent dsealing and indwelling did not happen until the new covenant was established!
Yes.
Acts 17:29-31
King James Version (KJV)
29 Forasmuch then as we are the offspring of God, we ought not to think that the Godhead is like unto gold, or silver, or stone, graven by art and man's device.
30 And the times of this ignorance God winked at; but now commandeth all men every where to repent:
31 Because he hath appointed a day, in the which he will judge the world in righteousness by that man whom he hath ordained; whereof he hath given assurance unto all men, in that he hath raised him from the dead.
Hebrews 9:11-15
King James Version (KJV)
11 But Christ being come an high priest of good things to come, by a greater and more perfect tabernacle, not made with hands, that is to say, not of this building;
12 Neither by the blood of goats and calves, but by his own blood he entered in once into the holy place, having obtained eternal redemption for us.
13 For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh:
14 How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God?
15 And for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance.
The Bible as a Whole teaches a very simple lesson, which is that God judges according to the revelation provided to men. Rejection of Christ will receive a far more severe penalty than rejection of the Covenant of Law (Hebrews 10:26-29, and sorry for not posting the Scripture for you, but out of time).
Take Passover, for example, in which we see God pass over those who were obedient. We do not ascribe eternal redemption or remission of sins in completion, because that sacrifice offered only pictured the Sacrifice of Christ, and would for centuries be offered until Christ came and offered Himself.
So when we apply the grace of God to children babies, and unborn babies, we see the same just and righteous dealing of God with mankind, in that He will judge according to the revelation provided to men in whatever Era or Age that revelation is found. Under Law one was to be obedient to the picture, figure, shadow, or parable of Redemption as found in the Law, but when the True came...they were to progress from that understanding formed by the revelation of that Age to that which was made perfect, or complete.
And we can draw a line in the sand in the sands of time, and agree with Christ that that time was when the Son of God stepped out of eternity and veiled His glory in human flesh. That flesh, the writer of Hebrews states, is the "veil" we go through in order to come into the presence of God.
So the question "Do babies go to Hell?" becomes moot in light of God's grace, because of course God will not penalize those who have not received revelation, and in regards to babies, and small children, and those mentally incapacitated...not even the internal witness of God and the testimony of Creation can fully (or at all) be realized by those individuals.
We serve a Righteous and Holy God, Who is Just. There is not one reason His Character can be compromised, or man seek to elevate themselves to a superior moral position (as atheists often do in their ignorance).
but would say that the born again experience for all believers, the permanent dsealing and indwelling did not happen until the new covenant was established
In the Old Testament this was a promise not yet fulfilled, and we see at every turn this realized in the pages of Scripture.
Eternal life is associated with the indwelling of the Comforter here:
John 7:38-40
King James Version (KJV)
38 He that believeth on me, as the scripture hath said, out of his belly shall flow rivers of living water.
39 (But this spake he of the Spirit, which they that believe on him should receive: for the Holy Ghost was not yet given; because that Jesus was not yet glorified.)
40 Many of the people therefore, when they heard this saying, said, Of a truth this is the Prophet.
The living waters are a contrast to physical water, without which one cannot sustain physical life. So too, apart from the indwelling of God, which could not take place as long as man was separated from God by their sins, eternal life cannot be attained to. John chapter 6 makes this contrast very well, between the physical and eternal provision of Old and New. And again we see that these promises were prophetic until fulfilled. They remained promise until fulfilled.
Those living waters are clearly stated to await the "giving of the Holy Ghost," and that event would not fall until Christ was glorified. Few will argue that the Baptism with the Holy Ghost preceded Pentecost, as they come into conflict with Christ's teaching in Act's 1:4-8.
And when they do, the arguments are weak, and they cannot find one person said to trust in the Gospel, or, the death, burial, and resurrection of Christ. I can give them the one who came closest, John the Baptist, but even he was not, just prior to his death...sure that Jesus was the One they awaited, though he was used of God to prophesy "the Lamb of God, which takes away the sins of the world."
God bless.