1.
Possession of moral knowledge or understanding is necessary before there can be accountability. There is no reason to fear that God makes children accountable at too early an age. He can be trusted to judge righteously:
Deut 1:39 ...and your children, which in that day had no knowledge between good and evil, they shall go in thither...
Isa. 7:16...For before the child shall know to refuse the evil, and choose the good...
Jonah 4:11...And And should not I spare Nineveh, that great city, wherein are more than sixscore thousand persons that cannot discern between their right hand and their left hand [most scholars understand this as a reference to children below 'the age of accountability']; and [also] much cattle?
2.
A baby's only real sin is the flesh/sinful nature. They are not be held accountable for wetting their diaper, making a mess when they eat or any other thing babies do. God at the same time does not hold a baby accountable because he has not believed on our Lord and Saviour. They have not reached an understanding yet, and are not accountable for such knowledge:
Romans 4:15....Because the law worketh wrath: for where no law is, [there is] no transgression.
3.
David was "a man after God's own heart." After he sinned with BathSheba, he fasted before God hoping to see the child of he and BathSheba spared. When the child died, David stopped fasting, got dressed and ate. He knew that he would go to his son one day -- the clear inference is that he would see his child in God's presensce -- in heaven:
2 Samuel 12:19-23...But when David saw that his servants whispered, David perceived that the child was dead: therefore David said unto his servants, Is the child dead? And they said, He is dead.Then David arose from the earth, and washed, and anointed [himself], and changed his apparel, and came into the house of the LORD, and worshipped: then he came to his own house; and when he required, they set bread before him, and he did eat.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.
4.
A person is only "spiritually alive" without the law before he or she is responsible and accountable. Paul understood this and made clear that in this sense, he was "alive" prior to the knowledge of his own sin through an understanding of God's Law:
Romans 7:8,9...But sin, taking occasion by the commandment, wrought in me all manner of concupiscence. For without the law sin [was] dead.For I was alive without the law once: but when the commandment came, sin revived, and I died.
5.
Thus, Paul was saying that as a child he was alive, (spiritually safe). But when he reached a certain age of maturity and understanding, he became spiritually dead in the knowledge of his sin. There are differences of opinion, but [IMO] this is not a specific age since all children mature at different rates. Some would take the very literal Jewish belief that accountability begins at age 13:
Romans 5:13...For until the law sin was in the world: but sin is not imputed when there is no law.
6.
Though a child is "guilty" of original sin, because they have neither knowledge of God's Law nor the ability to act according to knowledge and conscience, they are NOT held accountable for sin -- certainly not for the sin of those who have gone before:
Ezekiel 18:19-20... Yet ye say, Why? doth not the son bear the iniquity of the father? The soul that sinneth, it shall die; the son shall not bear the iniquity of the father, neither shall the father bear the iniquity of the son; the righteousness of the righteous shall be upon him,and the wickedness of the wicked shall be upon him.
7.
THe Lord Himself used "little children" as an example of the kind of attitude ALL must have in order to come to Him and enter His Kingdom. This was a poor metaphor on His part if it wasn't accurate and true:
Mark 10:14 - "Let the little children come to Me, and do not forbid them; for of such is the kingdom of God."
Matthew 19:14 - "Let the little children come to Me, and do not forbid them; for of such is the kingdom of heaven."
Matthew 18:3 - "Assuredly, I say to you, unless you are converted and become as little children, you will by no means enter the kingdom of heaven."
These passages, in my view, reflect a Biblical understanding of God's will -- and mercy -- toward children below the age of accountability. There is ample basis for the safety of children who die in infancy or before the age of accountability.
JDale