This was written before Christ walked this earth. That's basically what the Jews needed to do at that time to be in favor with God. After the crucifixion of Jesus, all bets are off on salvation by these means. Now you MUST accept Christ as the Savior. Hence John 14:6.
With the greatest respect, I would like to humbly disagree with this assessment. The Bible shows us that Jesus Christ was present with man since the beginning of creation. Humans have always had access to God the Son, and thus salvation has never been by any means except faith in Jesus Christ. Consider this: the Gospel is meant to be a good news. If Christ came to add an additional requirement to salvation (faith in himself), then this would not be good news at all. While the New Covenant has been fully revealed with the advent of Christ, salvation has never been possible without faith in him.
Now with regard to the Scripture in question, it's important to ask whether the Chronicler is teaching an absolute doctrinal statement, or not. As it says about the Law,
Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins. (Hebrews 9:22)
So here we are told that forgiveness was by the shedding of blood rather than prayer. The point here is not that the Bible contradicts itself. Rather the point is that it is easy to take a Scripture out of context, and form an incorrect doctrine on that basis. Here is an example from the New Testament:
If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. (1 John 1:9)
Much like the text from 2 Chronicles, one might asssume here that the forgiveness of sin, and indeed justification, requires only prayer and forgiveness of sin. Therefore I propose an alternate interpretation. We can note that the forgiveness of sin is directly tied to the healing of Israel's land. It's important to remember that in the Old Testament, theological terms like repentence, forgiveness, salvation, etc., are often tied directly to economic and military victories. Only later did these terms come to take on an added spiritual significance. If one reads the list of blessings and curses in the book of Deuteronomy, one will find that obeying the Law causes material blessing, while disobedience brings physical calamity. No mention of salvation is made, and this is why the Law cannot save. In this text, the forgiveness of sin involves
national repentence from idolatry and injustice, which will result in the physical blessing of good farming conditions. Seeing as how elsewhere God requires the sacrifice of animals, it clearly would not be appropriate to say that God requires only prayer and personal repentence for salvation (these are necessary but not sufficient conditions for salvation). Unfortunately, this is precisely the stance that modern Judaism has taken.
There are two responses that I would give to your Jewish friend. In the text, God uses the word "forever" only in his promise that the Temple will always stand. If we take this verse literally, then where is the Temple right now? We Christians know that God's promise applies to a heavenly Jerusalem, which Christ has bought at the price of his own blood. But Jews take the Bible literally when it is not meant to be taken literally, and here this clearly makes God out to be incorrect. The second response I would give to your friend is to ask how he deals with this commandment:
"Cursed be anyone who does not confirm the words of this law by doing them." And all the people shall say, "Amen." (Deuteronomy 27:26)
The Law requires a good deal more than prayer and repentence. Why would the Chronicler make a statement that contradicts the Law of Moses? It seems that the Jewish interpretation of the text doesn't work. In fact the Apostle Paul specifically quoted this same Scripture to show that the Law is not of faith. This is why salvation is by faith, and apart from works of the Law.
