Is it permissible for a Muslim man to give accommodation to a man who is a stranger or to host him in the marital home?

Ruling on students standing up for the teacher

Ruling on potlucks (get-togethers for a meal where each person brings something with him or her)

When a person enters upon other people, does he greet the oldest  first or the youngest?

Ruling on standing up for who comes in, and kissing him

Ruling on standing up to welcome a newcomer