Due to growing animosity between the pagan and Muslim Meccans in 622 AD, Muhammad and his followers fled to Medina, marking the beginning of the Hijra (Migration) era of the Islamic lunar calender and Muhammad's metamorphosis from a preacher to a political and military leader.
The 'right' of a family to wash its spoiled 'honor' by the 'misconduct' of another family member. This misbehaving includes being raped, thus loosing her hymen to a stranger, among the most horrible thing possible in an Islamic mindset.