La ilaha illa Allah, Muhammadu Rasool Allah.
—There is no deity except God, Muhammad is the Messenger of God.1
This is called the Shahadah الشهادة and is the Islamic confession of faith in a nutshell. They are the first words that every Muslim baby hears and they are often the last words a Muslim utters upon his deathbed. For nearly one billion people this is not merely a doctrinal creed—it is the foundation for every facet of their lives.
The Islamic faith is not simply an exotic Arabic religion. For many centuries it was virtually dormant, but over the last 50 years it has awakened and is spreading worldwide at an almost unprecedented rate.
If the Lord’s "Great Commission" is to be fulfilled it is essential that we, as active, concerned Christians, understand what Islam is. We must know both how to relate to the Muslim, and how to "contend for the faith which was once delivered unto the saints" (Jude 3), "with gentleness and reverence" (1 Pet. 3:15)
For more information, please refer to The Spirit of Islam site.