A commitment is a promise that is made by a lender to a buyer during mortgage negotiations. The commitment states in writing that the lender agrees to provide a loan to the buyer for a specific amount of time with specific terms. A commitment is often sent in the form of a letter from the lender to the buyer in which these terms are outlined in detail. The buyer can either accept the terms and enter into a mortgage or keep looking for another loan from another source. The commitment letter will often set a deadline by which the buyer must accept terms of the loan. In rare cases, the buyer can contact the lender and ask for better terms if the buyer feels there is additional evidence to the buyer's benefit that would improve the terms of the loan in the buyer's favor.