Maliks Muwatta Book 31, Hadith Number 15.

Yahya related to me from Malik that Abu’r-Rijal Muhammad ibn Abd ar-Rahman heard his mother, Amra bint Abd ar-Rahman say, “A man bought the fruit of an enclosed orchard in the time of the Messenger of Allah, may Allah bless him and grant him peace, and he tended it while staying on the land. It became clear to him that there was going to be some loss. He asked the owner of the orchard to reduce the price for him 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 Allah bless him and grant him peace, and told him about it. The Messenger of Allah, 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 it and went to the Messenger of Allah, may Allah bless him and grant him peace, and said, ‘Messenger of Allah, the choice is his.'”