You have an obligation to pay back. The ID card is the legal identification of every citizen. It is a legal contract for your friend to borrow money from the bank with your ID card. The parties to the contract are you and the bank. Although your friend actually borrows money from the bank, your friend is not a party to the loan contract. According to the principle of contract relativity, the bank has the right to ask you to repay the loan. Remind readers not to lend their ID cards casually, so as not to get into a lawsuit and harm their own interests.