What is the ruling on selling cosmetics to people, some of whom the seller knows will use them outside the home, or selling them with his knowledge that whoever claims to use them at home will use them outside of it?

The basic principle regarding the sale of cosmetics is permissibility, unless the seller knows that those who wish to purchase them will use them for forbidden purposes, such as displaying themselves adorned to non-mahram men. In such a case, it is not permissible for him to sell them, due to the Almighty's saying: (And cooperate in righteousness and piety, but do not cooperate in sin and aggression). However, if he does not know this, there is no impediment to the sale.