The true origin of the unity of the Islamic Ummah (society of all Muslims as a whole) is the religion of Islam, which derives its root from human nature. The changes that this religion has had over the course of history have been limited to the minor details of the laws which owing to the variety of the situations of human life in different societies.
The general principles that constitute the main body of the divine religion have always been united throughout history, this intellectual and ideological unity is the most important basis of unity in the Islamic society. In order to establish unity and solidarity among a community or nation, sharing common ideology and worldview are among basic necessities, without such a sharing, one can never expect a true unity among people.
Today, among more than one billion Muslims, there is no disagreement concerning God, the Book of God, and the Prophet of God, and the Qibla, which is the symbol of unity in the outside world, has never been disputed. These four basic principles of unity can always be counted on as reliable bases for solving all of the minor differences.