A:
It is not permissible for the father to pay Zakah of his money to his son, because
Zakah can not be given to one's descendants or ascendants. Also, Nafaqah (obligatory financial support) of your son is obligatory upon you. It is permissible for you to help him with money other than your due Zakah, in line with the general meaning of the Hadith in which the Prophet Muhammad (peace and blessings of Allah be upon him) said:
Whoever relieves a Muslim of one of the distresses of this world, Allah will relieve them of one of the distresses of the Day of Resurrection.
May Allah grant us success. May Peace and Blessings of Allah be upon our Prophet Muhammad, his family and his Companions!