My parents alwsys ask me to stay alert from strangers. They were right in their approach. Afterall, in this mean and selfish world, stranger could be quite dangerous. However at the same time, there are strangers too who comes out to help when we were in trouble in public places. This is normal human tendency to avoid a stranger. In fact we are bot comfortable with their presence. Either we look them as danger or we do not like their company. But, these strangers could be a boon to any situation. There is a noble words in Sanskrit that says :
परो अपि हितवान् बन्धुः बन्धुः अपि अहितः परः |
अहितः देहजः व्याधिः हितम् आरण्यम् औषधम् ||
Paro api hitavaana bandhuh bandhuh api haitah parah.
Ahitah dehajah vyaadhih hitam aaranyam aushadham.
Paro = others.
Api = even (to emphasise).
Hitavaan = beneficial, helpful.
Bandhuh = friend.
Ahitah = hostile, harmful.
Dehajah = existing in the body.
Vyaadhi = illness, disease.
Hitam = beneficial.
Aaranyam = herbs found in a forest.
Aushadham = medicine.
The lines simply means that, Even an unknown person is like a friend to you if he is beneficial and helpful to you, whereas a friend who is hostile or harmful to you is like a stranger to you. Similarly an illness or a disease in our body is harmful whereas a herb found in a remote forest (which can cure you) is beneficial to you.
These lines highlights, that it is not necessary that persons or things closer to us will always be beneficial. There are chances that even strangers who are helpful and beneficial are like your close friends. Be it any situation it is always advisable to stay aler, whenever we tend to get closer with any stranger before relying on them.