Growing up in church buildings, I heard the phrase "age of accountability" in passing when it concerned the death of a child, but never once did I hear any kind of teaching about what the Bible said concerning this matter, so I had no idea whether to take it as doctrine, or just something a pastor would say to make people feel better. As it turns out, there is Biblical authority for this doctrine, but because I have received so many letters over the years with people asking about it, I would conclude that most church buildings still aren't teaching properly on it, or their teachers don't know enough to do so.
The Lord Jesus Christ gave us a fairly good example of how swiftly and harshly he will judge those who harm children who believe on Him, and that we would need to, in our hearts, become humbled as little children to enter the kingdom of heaven.
At the same time came the disciples unto Jesus, saying, Who is the greatest in the kingdom of heaven? And Jesus called a little child unto him, and set him in the midst of them, And said, Verily I say unto you, Except ye be converted, and become as little children, ye shall not enter into the kingdom of heaven. Whosoever therefore shall humble himself as this little child, the same is greatest in the kingdom of heaven. And whoso shall receive one such little child in my name receiveth me. But whoso shall offend one of these little ones which believe in me, it were better for him that a millstone were hanged about his neck, and that he were drowned in the depth of the sea.
And the LORD God planted a garden eastward in Eden; and there he put the man whom he had formed. And out of the ground made the LORD God to grow every tree that is pleasant to the sight, and good for food; the tree of life also in the midst of the garden, and the tree of knowledge of good and evil.
And the LORD God commanded the man, saying, Of every tree of the garden thou mayest freely eat: But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.
For since by man came death, by man came also the resurrection of the dead. For as in Adam all die, even so in Christ shall all be made alive.
-1 Corinthians 15:22
Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned:
As it is written, There is none righteous, no, not one: There is none that understandeth, there is none that seeketh after God. They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one.
For all have sinned, and come short of the glory of God;
For when for the time ye ought to be teachers, ye have need that one teach you again which be the first principles of the oracles [i.e. prophets] of God; and are become such as have need of milk, and not of strong meat. For every one that useth milk is unskilful in the word of righteousness: for he is a babe. But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil.
Moreover your little ones, which ye said should be a prey, and your children, which in that day had no knowledge between good and evil, they shall go in thither, and unto them will I give it, and they shall possess it.
So then every one of us shall give account of himself to God.
I don't want anyone reading this to think that this exception God gives to babies and small children will apply to just anyone in general. Infamous athiest Richard Dawkins was interviewd in Expelled: No Intelligence Allowed by Ben Stein:
STEIN: "What if after you died you ran into God, and he says, what have you been doing, Richard? I mean what have you been doing? I've been trying to be nice to you. I gave you a multi-million dollar paycheck, over and over again with your book, and look what you did."
-Ben Stein, Expelled: No Intelligence Allowed, IMDB Quotes, retrieved Aug 20, 2016, [imdb.com/title/tt1091617/quotes]
What we have here is a typical atheist response in which they will claim ignorance as their defense. This will NOT work when standing before the Judgment Seat of God. Whereas a little child has true ignorance of the knowledge of good and evil, atheists like Dawkins are not ignorant; they only feign it to create an excuse as a last resort to justify themselves and their sinful lifestyles.
For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness; Because that which may be known of God is manifest in them; for God hath shewed it unto them.
For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse: Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened.
Professing themselves to be wise, they became fools, And changed the glory of the uncorruptible God into an image made like to corruptible man, and to birds, and fourfooted beasts, and creeping things. Wherefore God also gave them up to uncleanness through the lusts of their own hearts, to dishonour their own bodies between themselves: Who changed the truth of God into a lie, and worshipped and served the creature more than the Creator, who is blessed for ever. Amen. For this cause God gave them up unto vile affections: for even their women did change the natural use into that which is against nature:
And even as they did not like to retain God in their knowledge, God gave them over to a reprobate mind, to do those things which are not convenient; Being filled with all unrighteousness, fornication, wickedness, covetousness, maliciousness; full of envy, murder, debate, deceit, malignity; whisperers, Backbiters, haters of God, despiteful, proud, boasters, inventors of evil things, disobedient to parents, Without understanding, covenantbreakers, without natural affection, implacable, unmerciful: Who knowing the judgment of God, that they which commit such things are worthy of death, not only do the same, but have pleasure in them that do them.
For as many as have sinned without law shall also perish without law: and as many as have sinned in the law shall be judged by the law; (For not the hearers of the law are just before God, but the doers of the law shall be justified. For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves: Which shew the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another;) In the day when God shall judge the secrets of men by Jesus Christ according to my gospel.
The bottom line is those who are looking for the truth will find the Savior, and those who aren't will not.
I love them that love me; and those that seek me early shall find me.
Likewise, ye younger, submit yourselves unto the elder. Yea, all of you [i.e. Christians] be subject one to another, and be clothed with humility: for God resisteth the proud, and giveth grace to the humble.
The unbeliever has no excuse; feigning ignorance will not save them. They have the knowledge of good and evil, and they choose the evil, so they will be held accountable to the Lord God when Judgment Day comes.
I was investigating some other people teaching on this subject, and the most commonly quoted verse was this:
Then said his servants unto him, What thing is this that thou hast done? thou didst fast and weep for the child, while it was alive; but when the child was dead, thou didst rise and eat bread. And he said, While the child was yet alive, I fasted and wept: for I said, Who can tell whether GOD will be gracious to me, that the child may live? But now he is dead, wherefore should I fast? can I bring him back again? I shall go to him, but he shall not return to me.
-2 Samuel 12:21-23
Take heed that ye despise not one of these little ones; for I say unto you, That in heaven their angels do always behold the face of my Father which is in heaven. For the Son of man is come to save that which was lost.
(Read "Wolves in Costume: Amy Grant" here at creationliberty.com for more details.)
But to which of the angels said he at any time, Sit on my right hand, until I make thine enemies thy footstool? Are they not all ministering spirits, sent forth to minister for them who shall be heirs of salvation?
All this will certainly bring up the question: At what age does a little child enter into an age of knowledge of good and evil? I have no idea, and I don't believe it's the same age for every child because there are many circumstances that need to be considered.
There are some little children that are very wise and intelligent that may enter the age of accountability very early, and others who take much longer. There are also cases of mental retardation that need to be considered, in which case a child may grow into an adult and still not reach an age of accountability because they do not possess the mental reasoning to understand knowledge of good and evil.
It's because there is no set age that it is a very good idea to start children early on a Biblical foundation.
Train up a child in the way he should go: and when he is old, he will not depart from it.
Building up a solid Biblical philosophy (i.e. way of thinking) into a child is key for their understanding as they grow. When the child hears the message that all have sinned and come short of the glory of God, one day, the child will wake up with the understanding that he is part of those sinners. When the child is prepped with the understanding that the Lord Jesus Christ saves the lost, when they realize they're lost, they'll know where to turn; it's not a guarantee, but the chances are greater when they get the proper education early on.
To give an example, I gave a presentation at a church in which I reminded everyone that we were all going to die someday, and that we were not guaranteed to make it home. I said this posing the question, "If you died today, where would you end up?" An eight-year-old girl came up to me afterwards, told me that she realized she was not guaranteed another day in this world, and asked me how she could be saved. She believed on Christ was a saved, but after finding out some of her background, I realized that, although she was involved with Christian groups, she didn't have that basic understanding of the Gospel given to her, and once she was presented with the proper knowledge, she could make a clear decision.
Again, there is no specific age for accountability, and some situational factors need to be taken into consideration, but the good rule of thumb for most children is when they start asking about something, it's a good time to teach them. If you don't know when they will gain the knowledge of good and evil, then teach them about it beforehand, so when the time comes, they will know what to do.
Brethren, be not children in understanding: howbeit in malice be ye children, but in understanding be men.
-1 Corinthians 14:20