Sunan Ibn Majah, Chapter: The Chapters on Business Transactions

I used to send trade goods to Sham and Egypt, then I prepared to send trade goods to 'Iraq. I went to 'Aishah, the Mother of the Believers, and said to her: " O Mother of the Believers I used to send trade goods to Sham and I am preparing to send trade goods to 'Iraq." She said: "Do not do that. What is wrong with the way you have been doing it? I heard the Messenger of Allah (saw) say: 'If Allah causes provision to come to one of you through a certain means, he should not leave it unless it changes or deteriorates."