Abstract: Islamic banking in practice to implement financing one of them using Akad Murabahah, or commonly called bai 'al-murabaha. Akad which contains a number of rights and obligations for the parties, namely the Bank Syariah and the customer as the applicant Murabahah Financing Agreement. The financing is required by the customer, by purchasing the goods from the supplier and then selling them to the customer by adding a cost-plus profit and this is done through the first negotiation between the bank and the customer. In it contains an agreement that is the necessity of the principle of good faith. The goodwill underlying the formation of murabahah financing contract if the contract is made to fulfill the harmonious and contractual terms, then the contract has the binding strength as binding the Law. The contract can not be canceled other than the agreement of both parties or not contrary to the law, public order or morals, and the contract must be executed in accordance with the agreed, concerning good faith not only for the implementation of the agreement but also when the creation of the contract both parties should be based on good faith. With good faith in murabahah contract, it will fulfill the intention for both parties and the less chance of default in the contract.