Why do you think that charging interest is forbidden in the bible?

Deuteronomy 23:19 "You shall not charge interest to your brother--interest on money or food or anything that is lent out at interest. 20 To a foreigner you may charge interest, but to your brother you shall not charge interest, that the LORD your God may bless you in all to which you set your hand in the land which you are entering to possess.

Well, since the five Books of Moses was first given to the Children of Israel (the Jews), and it mentions that you should not take interest ftom your brother, it means Jews cannot charge another Jew interest.

When Adam and Eve ate the fruit, God punished them by throwing them out of the Garden of Eden. As their punishment, Adam would have to work for a living and Eve would have to bear children.

Ancient Hebrews believed it was wrong to get so rich that you didn't have to work, for your money to work for you. Of course like most religious beliefs, this belief took different forms at different times. I've read modern scholars who say that something like an investment in a company was okay, it was just lending money for interest that was wrong.

And of course all through history political leaders used religion for their own power, and when that happened the religious message would be modified to suit the ruling leader. So naturally it was not seen as a violation of the rule for the leader to borrow money to build up forces for an invasion or takeover, or to lend money to a leader for such purposes.

The Jews have to always remember that they were slaves in Egypt. They lived lives that was bitter and hard for them. God did not want any Jew to treat his brother like that remembering what they went through in Egypt. So charging interest would be treating their brothers like when they lived in Egypt. They could charge others interest but not the brothers.

I think the rule is that Jews are not allowed to charge interest when lending to each other. I would imagine the reason being that if your fellow man was poor enough to ask you to lend money to him you shouldn't profit off of his misfortune I guess unless it was a time of war but that I have not heard of.

Interest is a form of slavery. Look up Zeitgeist Addendum on YouTube. I don't endorse Z, but their explanation of our monetary system is an excellent and accurate explanation.

it was wrong to charge interest to the poor who had no money or to your fellow country me. You could charge strangers who were not jews but not your fellow jew.

Quite simply because everything belongs to God and He does not charge usury

Exd 22:25 If thou lend money to [any of] my people [that is] poor by thee, thou shalt not be to him as an usurer, neither shalt thou lay upon him usury.

Lev 25:36 Take thou no usury of him, or increase: but fear thy God; that thy brother may live with thee.

Lev 25:37 Thou shalt not give him thy money upon usury, nor lend him thy victuals for increase.

Deu 23:19 Thou shalt not lend upon usury to thy brother; usury of money, usury of victuals, usury of any thing that is lent upon usury:

Deu 23:20 Unto a stranger thou mayest lend upon usury; but unto thy brother thou shalt not lend upon usury: that the LORD thy God may bless thee in all that thou settest thine hand to in the land whither thou goest to possess it.

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Eze 22:12 In thee have they taken gifts to shed blood; thou hast taken usury and increase, and thou hast greedily gained of thy neighbours by extortion, and hast forgotten me, saith the Lord GOD.

Couldn't interest be charged on late payment for indulgences?

Boy did you misread that section. Reread and try again.