neither a borrower nor a lender be

The phrase "neither a borrower nor a lender be" is from William Shakespeare's play Hamlet, specifically from Act I, Scene III. It is part of a piece of advice given by Polonius to his son, Laertes, before Laertes leaves for Paris. The full quote is "Neither a borrower nor a lender be, for loan oft loses both itself and friend." The phrase advises against borrowing or lending money, indicating that both borrowing and lending can lead to troubles and complications. It suggests that one should avoid getting involved in financial obligations with others because such transactions can potentially harm relationships and cause one to lose not only money but also friendship.