The famous phrase "Neither a borrower nor a lender be” is said by Polonius in Act-I, Scene-III of William Shakespeare’s play, Hamlet. The character Polonius counsels his son Laertes before he embarks on his visit to Paris. He says,

"Neither a borrower nor a lender be,

For loan oft loses both itself and friend,

And borrowing dulls the edge of husbandry".

It means do not lend or borrow money from a friend, because if you do so, you will lose both your friend and your money. If you lend, he will avoid paying back, and if you borrow it will come out of your savings, and you can turn into a spendthrift and face humiliation.

In the final scene, Laertes kills Hamlet with a poisoned sword to avenge the deaths of his father and his sister Ophelia, for which he blamed Hamlet. While dying of the same poison, he implicates King Claudius. Also, this phrase refers to Laertes, who, with a poison-tipped sword, injures Hamlet and then exchanges swords accidently with Hamlet and is poisoned by his own sword. In this way, he is a lender and borrower of swords. A lent sword kills him during his fight for a borrowed cause.

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