Praise be to Allaah.
It is not permissible for you to buy anything for your
father which it is haraam to use, whether it is tobacco, opium, hashish,
alcohol or whatever, even if he tells you to do that. It was reported that
(peace and blessings of Allaah be upon him) said:
“There is no obedience to any created being if it involves disobedience
of the Creator” and, “Obedience is only with regard to things which
are right and good (ma’roof).” You have to advise him and
apologize to him politely for not buying them for him.
Sheikh Muhammed Salih Al-Munajjid