Reference: Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-‘Ilmiyyah wal-Iftaa. – Volume 13, Page 64, Question No.4 of Fatwa No.3201
Question: Is it permissible for me to buy tobacco (cigarettes) for my father as he orders me to do so?
Response: It is not permissible for you to buy anything for your father whose use is haraam, be it cigarettes, opium, drugs (narcotics), alcohol or other than this. This is because it is confirmed from the Prophet (sal-Allaahu ‘alayhi wa sallam):
«There is no obedience to [any of] the creation whilst committing a sin against the creator».
And his (sal-Allaahu ‘alayhi wa sallam) saying:
«Certainly, obedience is in [all that is] good».
So, it is upon you to advise and offer him an excuse against buying them with good manners.
And with Allaah lies all success and may Allaah send prayers and salutations upon our Prophet (sal-Allaahu ‘alayhi wa sallam) and his family and his companions.