Increase in item sold

Question

After the completion of a sale, is it permissible to increase in the item sold (i.e. add on to the agreed quantity) or to increase in the exchange (i.e. pay more than the agreed price)?

zd · Answer

It is permissible for the buyer to give more money to the seller, or for the seller to increase in the quantity of the item sold to the buyer (Kitaabul Buyoo).