“This "Clash of Civilizations" has led to a "Clash of Religions", leading in turn to war, terror and extreme poverty.”

Source: The Clash of Civilizations and the Remaking of World Order (1996), Ch. 12 : The West, Civilizations, and Civilization, § 4 : The Commonalities Of Civilization, p. 321
Context: The futures of both peace and Civilization depend upon understanding and cooperation among the political, spiritual, and intellectual leaders of the world’s major civilizations. In the clash of civilizations, Europe and America will hang together or hang separately. In the greater clash, the global “real clash,” between Civilization and barbarism, the world’s great civilizations, with their rich accomplishments in religion, art, literature, philosophy, science, technology, morality, and compassion, will also hang together or hang separately. In the emerging era, clashes of civilizations are the greatest threat to world peace, and an international order based on civilizations is the surest safeguard against world war.

International Business and Leadership Symposium address

"The Clash of Civilizations?," in Foreign Affairs (1993)
Context: It is my hypothesis that the fundamental source of conflict in this new world will not be primarily ideological or primarily economic. The great divisions among humankind and the dominating source of conflict will be cultural. Nation-states will remain the most powerful actors in world affairs, but the principal conflicts of global politics will occur between nations and groups of different civilizations. The clash of civilizations will dominate global politics. The fault lines between civilizations will be the battle lines of the future.

360 Doctrines and Comprehensive Theories, Union of Civilizations

Frankfurt Book Fair speech (2003)
Context: All modern wars, even when their aims are the traditional ones, such as territorial aggrandizement or the acquisition of scarce resources, are cast as clashes of civilizations — culture wars — with each side claiming the high ground, and characterizing the other as barbaric. The enemy is invariably a threat to "our way of life," an infidel, a desecrator, a polluter, a defiler of higher or better values. The current war against the very real threat posed by militant Islamic fundamentalism is a particularly clear example.

[We Must Continue What Dink Started: Dialogue with Turkey, Says Bishop, Tert.am, 2010-02-15, http://tert.am/en/news/2010/02/15/bishop/, 2010-02-16, English]
Other

2000s, 2004, Speech to United Nations General Assembly (September 2004)

As quoted in “Michael Burleigh: The reluctant guru,” John Crace, The Guardian, March 10, 2008 https://www.theguardian.com/education/2008/mar/11/academicexperts.highereducationprofile

Presidential campaign (April 12, 2015 – 2016), Speech on fighting ISIS (November 20, 2015)