سنن النسائي

It was narrated that Abu Hurairah said: "I heard the messenger of Allah say: "No man should urge anyone to cancel a sale he has already agreed upon with his brother so as to sell him his own goods; no town-dweller should sell for a desert-dweller; do not artificially inflate prices; no man should outbid his brother; and no woman should ask for her sister (in faith) to be divorced so as to turn over what is in her vessel (deprive her of her share of maintenance),