I really don't think Scripture deals with it. It is my understanding that Christianity adopted AOA from Jewish tradition. This is not in C vs A forum, so I won't go there. All I can say is the elect had their name written in the book before the foundations of time. It is a mystery left in the hands of God.
I beileve that Romans 5 makes a good case namely with the phrase "sin is not imputed where there is no law." It is further understood that we have both the written laws of Moses as well as the natural laws written in our conscience (Rom 2). There are also the "invisible things of him from the creation of the world which are clearly seen" (Rom 1:20) which also bears witness and renders a man to be without excuse. From here, we need to ask the question:
at what point is a person cognizant of that which is clearly seen whereby they are culpable and without excuse? Of what awareness does a newborn infant have regarding such things? We also have an interesting observation from Paul where he says "I was alive without the laws once but when the commandment came, sin revived and I died" (Rom 7:9).
You do not want to go into a "C vs A" debate and neither do I but this does become a hot topic in such a debate does it not? I remember Leighton Flowers just about going into "Full Meltdown" mode during a debate with James White over Calvinists condemning babies to hell but he was either completely ignorant of the topic or he was trying to emotionally manipulate the audience. Flowers is far from being ignorant so I would have to assume the latter but such is neither here nor there but what is clear is that he blatantly misrepresented the view of most Calvininsts!
The reformed crowd often pokes fun at Baptists regarding the so-called "age of accountability" but such is clearly taught with their "Federal View" which is cornerstone to their covenant theology and of which I would largely agree! I am not going to get into a big dissertation here but with a few keystrokes in a search engine, one may study this out for themselves and compare Federalism (Covenant Theology) with Seminalism (Roman Catholic and Lutheran position) which actually does damn unbaptized infants either to limbo or Hell.
I wonder if there was a certain age at which a child growing up in OT Israel would be considered personally responsible and of which he or she would bring their own sin offering to the temple? Perhaps this is where the tradition of the Bar (Bat) Mitsvah comes into play.
I believe it wrong if not dangerous to decree as specific age as being the "Age of Accountability" as such would be different for every individual. When one first comes to the realization that they are a sinner and therefore guilty before God, this would be their "Age of Accountability" and the individual is responsible to God in regards to how they deal with this. As a child growing up in Roman Catholicism, I started attending catechism classes (CCD) in preparation for the Sacrament of Pennance and my "First Communion" and I would guess that at such a time, a child would probably fall from the "state of grace" of their baptism and would therefore need to be restored through the sacraments of penance and the eucharist. Baptists often pressure kids into some sort of "Decision" in their grammar school years and kids often go through the "Pray the sinners prayer and ask Jesus into their heart" ritual without fully understanding the implications aside from the fact that all of their other friends are doing it.
