What is the ruling on entering a mosque with a cigarette pack in one's pocket?

Tobacco (smoking) is forbidden and harmful, but it is not impure. Not everything that is forbidden is impure. Prayer is valid while carrying it, and there is no obligation to wash clothes that come into contact with it, as the Malikis and Shafi'is have affirmed its purity. Carrying tobacco into the mosque is not permissible because it contradicts the reverence due to the houses of Allah. However, the prayer of someone from whom tobacco has fallen is valid. Everything impure is forbidden, but not everything forbidden is impure. Poison, for example, is forbidden but not impure, and tobacco is forbidden but not impure.