A marriage contract must fulfil the following conditions [for it to be valid]: 1. based on obligatory precaution, the formula must be said in Arabic. If the man or the woman is unable to say the formula in Arabic, they can say it in a language other than Arabic, and it is not necessary that they appoint an agent; however, they must use words that convey the meaning of زَوَّجْتُ [zawwajtu] and قَبِلْتُ [qabiltu]; 2.
If their agents say the formula, then when they say زَوَّجْتُ [zawwajtu] and قَبِلْتُ [qabiltu], they must intend for the man and the woman who have appointed them as their agents to become husband and wife; 3. the person saying the formula must be sane (ʿāqil). If the person is saying it for himself or herself, he/she must also be of the age of legal responsibility (bāligh).
In fact, based on obligatory precaution, if a non-bāligh child who is able to discern between right and wrong (mumayyiz) says the formula for someone else, it is not sufficient, and the couple must get a divorce or repeat the formula; 4. if the agent of the man and woman, or their guardians (walīs), say the formula, then at the time of the contract, they must specify the husband and wife. For example, they must mention their names or indicate to them.
However, if they appear to disapprove but it is known that in their hearts they consent, the marriage contract is valid.