According to Proverbs 22:7, the borrower is slave to whom?

Answer: The lender

Proverbs 22:7: "The rich rule over the poor, and the borrower is slave to the lender" (KJV: "servant to the lender").

“The rich rule over the poor, and the borrower is slave to the lender.”— Proverbs 22:7 (BSB)