Scripture reminded the Israelites to "train up a child in the way he should go" (via their Schema, Deut..6) in the hope that "when he is old(er) he will not depart from it" Prov. 22:6
Reminding Pastor Timothy of that time in his childhood, the Apostle Paul writes...
2 Timothy 3:14 But continue thou in the things which thou hast learned and hast been assured of, knowing of whom thou hast learned them; 3:15 And that from a child thou hast known the holy scriptures, which are able to make thee wise unto salvation through faith which is in Christ Jesus.
In other words, because children do not know right from wrong; they require instruction on both.
That they might come to know the difference between the two "by reason of use" Heb. 5:14.
However, that does not mean they are "innocent" or "pure."
It means they do not know right from wrong, not that they do not do right and wrong.
It means they do not know right from wrong.
(And that moment of first knowing the difference, is different for each child).
Were they "innocent" or "pure" Christ would not have had to die.
But He died because all humanity is precious to The Father, 1 Peter 3:20; 2 Peter 3:9, etc.
And children also fit in said "precious" category.
But especially children.
Why?
Because those "children being not yet born, neither having done any good or evil," are, after they are born, not counted as being in rebellion against God until that point wherein they are able not only to discern between good and evil, but to knowingly choose between the two.
Until then, said child has not knowingly and willingly gone against "the purpose of God" as to this issue - "Who will have all men to be saved, and to come unto the knowledge of the truth" 1 Timothy 2:4.
For just as with the issue of Election, Romans 9:11 (when properly understood) salvation is also not only "Not of works, lest any man should boast" Ephesians 2:9, but said child's works, are not yet even an issue with God, because the little tyke does not yet know the difference between right and wrong.
In short, if we are so cut a break by God that
"when we were yet without strength, in due time Christ died for the ungodly" Romans 5:6, you know He is going to "suffer the little ones" even more so.
I, for one, do not mind in the least, His "respect of persons" where said little ones are concerned.
Matthew 18:10 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.
Matthew 18:14 Even so it is not the will of your Father which is in heaven, that one of these little ones should perish.
Thus why - Romans 5:8 - Amen!