Ulum al Qur'an
How it came about
When the message of Islam was presented to the Arabs as something new, and different from their way of life, it was introduced in stages. The Qur'an brought important changes gradually, to allow the people to adjust to the new prescriptions.
Example:
There are three verses in the Qur'an concerning the drinking of wine. Wine drinking was very widespread in pre-Islamic times and, although a social evil, highly esteemed. The three verses which finally led to the prohibition of intoxicating substances were revealed in stages (4: 43, 2: 219; 5: 93-4).