1. Once the sale is concluded, neither the purchaser nor the seller has the right to unilaterally cancel the sale. However, if the customer wishes to return the purchased item and cancel the sale, it will be greatly rewarding for the seller to cancel the sale and give him a full refund.
عن أبي هريرة رضي الله عنه قال قال رسول الله صلى الله عليه وسلم: من أقال مسلما أقاله الله عثرته يوم القيامَة. (ابن ماجه رقم 2199) وفي رواية صحيح ابن حبان (رقم 5029) من أقال نادما بيعته أقال الله عثرته يوم القيامة.
Hazrat Abu Hurayrah (Radhiyallahu Anhu) reports that Rasulullah (Sallallahu Alaihi Wasallam) said, “The one who cancels the sale for a Muslim (upon his request), Allah Ta’ala will forgive his sins on the day of Qiyaamah.”
In one narration, Rasulullah (Sallallahu Alaihi Wasallam) mentioned, “The one who cancels the sale for a person who regrets the sale, Allah Ta‘ala will forgive his sins on the Day of Qiyaamah.”