why is it bad to borrow or lend? If I borrower to invest and my profit is higher than the interest rate I borrow, I make a profit. If I have excess money, I can lend it out and charge interest. Why do people say neither a borrower nor a lende be? I can profit from doing both. Where did this come from?

That's from Shakespeare, in Hamlet. It's a man's advice to his son. He means, don't borrow from or lend to friends.

To borrow money to invest is a very bad idea.

What will you do if you lost money investing?

It's biblical advice and it's good advice. Your best bet is to develop a long and short term plan and stick to it.

Historically, it was considered immoral to charge interest on money.

Here is a decent article:

https://www.theobjectivestandard.com/iss...

Those are big "IFs"