What is the Prophetic Sunnah regarding trade, describing goods, exchanging them, and returning them?

The Prophet's guidance (peace and blessings be upon him) in trade, selling, and buying can be summarized in the following points:

1. His engagement in trade before and after his prophethood, and his direct involvement in selling himself or entrusting his companions to do so. 2. His command to traders to be righteous and truthful, to speak the truth and clarify, and to mix their sales with charity. 3. His command for leniency and ease in selling and buying. 4. His urging to fulfill rights due to their owners with excellence. 5. His urging to cancel transactions for those who regret them. 6. His bargaining in buying and not devaluing people's merchandise. 7. His command to give full measure when weighing. 8. His command to grant respite to the one in hardship or to waive the debt for him. 9. His prohibition of dealing with usury (riba), gharar (uncertainty) sales, 'eenah (buy-back) sales, trading in forbidden items, and cheating and deception.