For a sale to be valid, several conditions must be met. Some pertain to the contracting parties, others to the subject‐matter of the contract. If any required condition is missing, the sale is invalid.

Conditions related to the contracting parties

1. Mutual consent. A sale is not valid if either party is unlawfully coerced. Allah, Exalted is He, says, “…except it be trade conducted by mutual consent among you” (Qur’an 4:29). The Prophet ﷺ said, “A sale is only concluded with mutual consent,” recorded by Ibn Ḥibbān, Ibn Mājah, and others. Should the coercion be lawful—such as when a judge compels a debtor to sell property to settle his debt—the sale is valid, for this is legitimate compulsion.

2. Legal capacity. Each party must be legally competent to transact, meaning free, of sound mind, and mature. Therefore, a sale concluded by a minor, a prodigal, an insane person, or a slave without his master’s permission is invalid.

3. Ownership or agency. Each party must own the item being transacted or act on behalf of its owner. The Prophet ﷺ said to Ḥakīm ibn Ḥizām, “Do not sell what you do not possess,” related by Ibn Mājah and al-Tirmidhī, who declared it sound; that is, do not sell property that is not yet in your ownership.