From “How to become a Christian”: Chapter 8 – More bad news – Judgment, Hell and the Lake of Fire in closer detail
I feel that I ought to add a brief explanation about children, and what happens when they die. Strictly speaking, the Bible does not directly address this question. Nor does it define what a ‘child’ is exactly, i.e. what age childhood goes up to. Presumably the age of responsibility for one’s own sin varies from child to child, depending on their level of knowledge and circumstances. We are not told. We can however look at 2 Samuel chapter 12, which refers to the death of King David’s baby son:
21His servants asked him, “Why are you acting this way? While the child was alive, you fasted and wept, but now that the child is dead, you get up and eat!” 22He answered, “While the child was still alive, I fasted and wept. I thought, ‘Who knows? The LORD may be gracious to me and let the child live.’ 23But now that he is dead, why should I fast? Can I bring him back again? I will go to him, but he will not return to me.”2 Samuel 12:21-23 (NASB)
Note that King David says “I will go to him, but he will not return to me”. That is a very important indicator of what had happened to that baby. We know, because the Bible makes it clear elsewhere, that King David was saved and has now gone to Heaven. King David himself knew that he was going to go to Heaven. So, when he said “I will go to him” he meant he would see his dead child again in Heaven, i.e. after his own death. That seems very clear.
So, if anybody reading this has lost a young child, you have a valid basis to be comforted by King David’s words. The above passage strongly suggests that the child is safe and has eternal life. The reason why a young child is not condemned is, presumably, because they are not yet at the age of accountability i.e. where they become responsible for their own sins. Prior to that they are, evidently, deemed to be innocent. That is my understanding.
But what is the exact age of accountability or responsibility? The Bible does not tell us. However, Jewish tradition, which may be an indication, is that it is at the age of 12 or 13. That is when a Jewish child has its Bar Mitzvah and becomes legally an adult. At that point they are said to become responsible for their own sins. Whether that is the actual age or not, I do not know. Only God knows that. I expect it varies from child to child, according to their knowledge and maturity.