Is it permissible to buy razors for someone knowing that he will use them to shave his beard, and what if this person is your father, and he finds difficulty buying razors himself due to his old age and illness?

It is not permissible to help anyone commit a sin or an unlawful act, for this falls under aiding in sin and aggression, which is forbidden by His Almighty's saying: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." If the person is a parent, they should be advised in a friendly manner, explaining that shaving the beard is not permissible, while emphasizing that assisting in sin is aiding in transgression. It is not permissible to seek the pleasure of creatures by incurring the wrath of the Creator, for obedience to parents is obligatory in what Allah has permitted, and not permissible in what is forbidden.