(Fatwa: 2051/D=457-File D=1432)
If one’s father orders against the fardh and wajib commands of the Almighty Allah or asks to commit any haram and sinful act then it is not lawful to obey father in this case. It is fardh to obey Almighty Allah.
لا طاعة لمخلوق فى معصية الخالق .
But you should behave him politely and in good manner. Do not disrespect him. Never show harsh attitude or use tough words. If you find time to say your words then speak him directly with respect or with the mediation of your mother. Also keep on supplicating for him.
رَّبِّ ارْحَمْهُمَا كَمَا رَبَّيَانِي صَغِيراً
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband