Yahya related to me from Malik that Abu'r-Rijal Muhammad ibn Abdar-Rahman heard his mother, Amra bint Abd ar-Rahman say, "A man boughtthe fruit of an enclosed orchard in the time of the Messenger ofAllah, may Allah bless him and grant him peace, and he tended it whilestaying on the land. It became clear to him that there was going to besome loss. He asked the owner of the orchard to reduce the price forhim or to revoke the sale, but the owner made an oath not to do so.The mother of the buyer went to the Messenger of Allah, may Allahbless him and grant him peace, and told him about it. The MessengerofAllah, may Allah bless him and grant him peace, said, 'By this oath,he has sworn not to do good.' The owner of the orchard heard about itand went to the Messenger of Allah, may Allah bless him and grant himpeace, and said, 'Messenger of Allah, the choice is his.' "
USC-MSA web (English) reference: Book 31, Hadith 15
Arabic reference: Book 31, Hadith 1308