Question 12: I married one of my daughters to a man whom I did not ask to pay a Mahr (mandatory gift to a bride from her groom). One year after their marriage my son-in-law gave me a Toyota (car) though I did not ask him to do so. What is the ruling on this?
Answer: It is permissible for you to take the car from your son-in-law. If he gave it to you as a Mahr, it should go to your daughter. However, if he gave it to you as a gift; you may take it for yourself but your son-in-law has to pay a proper Mahr to your daughter if he did not do so at the time of the conclusion of the marriage contract... read more here.