Negative Mitzvah 237
It is forbidden to participate in a loan in which interest is charged
Exodus 22:24 "Neither shall you take interest from him"
This Negative Mitzvah cautions us not to take part in any deal or loan that involves interest.
For example: We may not serve as guarantor (person responsible if the borrower doesn't pay) or a witness in such a deal.
Nor may we provide our services to write up the contract between the borrower and lender.