To the third and fourth generation...

Someone asked a question last night - why in Neh 9 do they pray for the sins of their fathers?

here's a suggestion - referencing the third and fourth generation passing of sin in the 10 commandments:

Deuteronomy 23:7-8 7 "You shall not abhor an Edomite, for he is your brother. You shall not abhor an Egyptian, because you were a sojourner in his land. 8 Children born to them in the third generation may enter the assembly of the LORD.

things up to the 3rd and 4th generation symbolise the inherentness of something
so an Edomite or Egyptian 3-4 generations later becomes an Israelite - proving that this is his true nature

similarly for sin:
Exodus 20:5 5 You shall not bow down to them or serve them, for I the LORD your God am a jealous God, visiting the iniquity of the fathers on the children to the third and the fourth generation of those who hate me,

for example.. Cain is a murderer - now Lamech is the 4th from Cain - is also a murderer
implying the inherent violence in the human race- that will cover the whole earth (cf. Gen 6:11)

also in the book of Amos, the accusations against the nations are like this:
Amos 1:3 For three transgressions of Damascus, and for four, I will not revoke the punishment,
Amos 1:6 "For three transgressions of Gaza, and for four, I will not revoke the punishment,
etc

So as you were saying last night..
the sins of our fathers admission is a demonstration that we know the inherentness of sin and the proneness of the flesh

now it is not that this causes us to 'blame them'
therefore in Ezekiel 18 - this is the case:
Ezekiel 18:2-3 2 "What do you mean by repeating this proverb concerning the land of Israel, 'The fathers have eaten sour grapes, and the children's teeth are set on edge'? 3 As I live, declares the Lord GOD, this proverb shall no more be used by you in Israel.
and the rest of the chapter

in this case - we are using the 'it's not our fault' argument - it's their fault

but the humble sinner recognises the inherentness of sin within himself, knowing that he will do the same sins of the fathers left unchecked - and so in Neh 9-10, enters into the covenant promise of the Lord - with a true repentance (cf. 2 Cor 7)

In fact those that understand this pray for the sins of others - e.g. Nehemiah, Moses, Jesus, Job, etc...

there is one other time this 3/4 thing is used - Prov 30
blackham has a post on that
not sure if it ties up with this!