Hazrat Shurayh (may Allah have mercy on him) says that if there is a dispute between the seller and the buyer and the sold item is still present as it is, then witnesses will be requested from both. If either of them presents witnesses, it will be given to him on account of his witnesses. And if neither of them has witnesses, then both will be made to take an oath. If both take an oath, the sale will be annulled. And if both refuse to take an oath, the sale will also be annulled. And if one takes an oath while the other refuses, then it will be given to the one who took the oath. And if the sold item is not present as it is or it has perished, then the seller will be required to present witnesses and the buyer will be required to take an oath.