Maliks Muwatta Book 31, Hadith Number 19.

Yahya related to me from Malik from Abu’r-Rijal, Muhammad ibn Abdar-Rahman ibn Haritha that his mother, Amra bint Abd ar-Rahman used to sell her fruit and keep some of it aside.

Malik said, “The generally agreed upon way of doing things among us is that when a man sells the fruit of his orchard, he can keep aside up to a third of the fruit, but that is not to be exceeded. There is no harm in what is less than a third.”

Malik added that he thought there was no harm for a man to sell the fruit of his orchard and keep aside only the fruit of a certain palm-tree or palm-trees which he had chosen and whose number he had specified, because the owner was only keeping aside certain fruit of his own orchard and everything else he sold.