Is it permissible for a man to register a portion of his property in his wife's name to secure her future and that of their children, and would this affect the inheritance in the event of his death, given that his father is alive?

It is Islamically permissible for a man to gift his wife whatever he wishes from his money and possessions, provided he is legally competent and of sound mind, and that the gift is given willingly, even if the intention is to please and reassure her. This excludes cases where the intention is to disinherit heirs or harm them, based on the Prophet's (peace be upon him) saying: "There shall be no harm nor reciprocating harm."

The gift becomes the wife's property upon her taking possession of it. If possession has not been taken and the husband dies, the gift reverts to his estate for his heirs. Ibn Abi Zayd al-Maliki said: "Neither a gift, nor a charity, nor an endowment is complete except by taking possession."

If the man has other wives, he should also gift them out of fairness, though some scholars believe that equality in gifting among wives is not obligatory. As for alleviating the wife's fears, this is done by reassuring her and gaining her trust, and by instilling trust in Allah and reliance upon Him.