Is it permissible for the husband to complete the amount of his wife's vow of sacrifice from his own money if she has income from an inheritance but does not have enough money to fulfill the vow?

There is no harm for the husband in financially assisting his wife to fulfill her vow, as that is helping in righteousness, based on the Prophet’s (peace and blessings be upon him) saying: "Allah is helping the servant as long as the servant is helping his brother." And based on his saying: "Whoever among you is able to benefit his brother, let him do so." And there is no harm for her in accepting this gift.