Why Hijab?

السلام عليكم

بِسْمِ اللهِ الرَّحْمنِ الرَّحِيمِ

O Prophet! Tell thy wives and thy daughters and the women of the believers to draw their cloaks close round them (when they go abroad). That will be better, so that they may be recognised and not annoyed. Allah is ever Forgiving, Merciful.

(33:59)