What is the ruling of Islamic law on spending on a father who does not spend money on the household and uses it to buy cigarettes and alcohol, knowing that he does not harm anyone? And am I sinful if I stop spending on him?

It is obligatory to be dutiful to one's father by being benevolent towards him with money and influence, and he has the right to be financially supported by his child, as the Messenger of Allah, peace and blessings be upon him, said: "You and your wealth belong to your father." However, if it is highly probable that the father will use the money for something forbidden, such as alcohol or smoking, then it is not permissible to give him more than what is necessary for his maintenance. In fact, refraining from doing so is an act of dutifulness towards him, as the Prophet, peace and blessings be upon him, said: "Help your brother, whether he is an oppressor or oppressed," - until he said: "to prevent him from oppressing." It is also advisable to counsel him, warn him about the consequences of alcohol and smoking, and supplicate for his guidance.