All praise is due to Allah, Lord of the Worlds, and peace and blessings be upon our Master Muhammad, the Seal of the first and the last, and a mercy to the worlds.

Professionals and craftsmen such as carpenters, tailors, and those who work in vehicle maintenance and the like, are categorized by the jurists as Joint Employees (Ujarā’ Mushtarakūn). The Joint Employee is one who accepts work from more than one person. These employees are held liable (guarantors, ḍāminūn). This is the doctrine of the Ḥanafī school and an opinion within the Shāfi'ī school. It was explicitly stated in the Majallat al-Aḥkām al-'Adliyyah (Ottoman Civil Code) in Article (611): "The Joint Employee guarantees the harm and losses that arose from his action and description, whether or not they resulted from his transgression or negligence."

Imam Al-Bābartī al-Ḥanafī justified the ruling of liability (taḍmīn): "Because holding the Joint Employee liable is a type of legal preference (istiḥsān) according to the Two Companions [of Abū Ḥanīfah]; it is to protect people's wealth. He accepts many items because of his desire for a high fee, and he may become unable to fulfill the right of custody over them. Therefore, he is held liable so that he does not become negligent in protecting them, and so that he only accepts what he is capable of safeguarding." (Al-'Ināyah Sharḥ al-Hidāyah, Vol.9/P.129).

Thus, the liability of the Joint Employee for what is damaged is restricted by three conditions as mentioned in Ḥāshiyat Ibn 'Ābidīn:

1. That the removal of the cause of damage is within his (the Joint Employee’s) capability. For instance, if [the goods] were submerged by a wave, a wind, or the impact of a mountain, he is not liable.

2. That the place of work has been handed over to him by vacating the premises (i.e., that he has full control). If the owner of the goods or his agent is on the ship [or premises], he is not liable.

3. That the guaranteed object is something permissible to guarantee by contract. Therefore, a human being is not guaranteed. (Ḥāshiyat Ibn 'Ābidīn 'alā ad-Durr al-Mukhtār, Vol.6/P.66).

In conclusion, if the owner of the vehicle gives his vehicle to the owner of a maintenance garage (mechanic), the vehicle enters the liability of the garage owner. He guarantees everything that is damaged while in his custody because he is a Joint Employee. No liability falls upon the vehicle owner, unless the damage resulted from an unavoidable accident. And Allah the Almighty knows best.