What is the ruling on someone who bought used clothes and a small stain appeared on them after four days? Is the seller entitled to refuse to return them unless the buyer comes to him?

If the buyer's right to return due to a defect is established, the expense of returning the sold item falls on the buyer, unless the seller defrauded the buyer, in which case the expense shifts to the seller. This is because ownership transfers from the seller upon his choice to return the item, and thus the right to a full refund becomes attached to him. However, the buyer is not obligated to bear the expense of the return if the seller of the item committed deception.