Is it considered a sin to refuse a person who asks for a large sum of money, while I am in need of it for marriage?

A goodly loan (Qard Hasan) is something encouraged by Islamic law, which promises a great reward for it. It is recommended for the lender and permissible for the borrower, as it alleviates distress for a Muslim. A loan is not obligatory, and one who refuses it does not incur sin, especially if the lender needs the money or fears the borrower will not repay. Thus, there is no blame on one who does not offer a loan, because it is not a legal obligation.