The first and foundational pillar of Islam is called the shahada, or the confession of faith. This simple creed says, “There is no god but Allah, and Muhammad is the Prophet (or messenger) of Allah.” Someone is considered a Muslim if they sincerely believe and recite this simple phrase in Arabic.

Shia Muslims, who comprise around 10-13% of all Muslims, add another clause that says, “And Ali is the friend (or holy man) of Allah.” Ali, a cousin and son-in-law of Muhammad, is revered and recognized by Shia as Muhammad’s first successor after his death in 632 AD.

On one hand, becoming a Muslim is that simple. On the other hand, the shahada is packed with meaning and significance. The complete shahada is not found in any one verse in the Quran. It is a combination of statements found in many verses of the Muslim holy book which focus on Allah’s oneness and on Muhammad as Allah’s messenger.

It reinforces that Muslims should only worship Allah, and it is Muhammad’s example Muslims should follow. The oneness of Allah, known as tawhid, is supreme in Islamic belief. Everything else follows from this central and critical understanding. The Quran says in chapter 4 verse 48 that worshiping anyone or anything else other than the one true God is idolatry. It is the unforgivable sin.

The shahada provides a simple yet effective means of faith cohesion among the world’s 1.8 billion Muslims. No matter where in the world Muslims come from, no matter their language or culture, they are Muslims if they genuinely believe and confess this statement of faith.

 Sadly, sometimes the shahada is a matter of life and death. It distinguishes believers from unbelievers, so groups like Boko Haram will force individuals to prove their allegiance – and preserve their very lives – by reciting it.

In Islam, the written word developed as an art form.

While it is considered sacrilegious to picture the human form, words are central in Islamic art. The text of the shahada can be found in beautiful calligraphy on everything from buildings to black velvet wall hangings. The inner and outer walls of mosques are often decorated with gorgeous renditions of the confession of faith, oftentimes in stunning shades of blue. It adorns jewelry, printed materials, and even state flags (the flag of Saudi Arabia carries the complete confession of faith in white calligraphy against a green background).

The shahada is central to the Muslim call to prayer. It rings out over millions of loudspeakers from mosques around the world five times a day. Some of the faithful even wear programmed watches and know when it’s time to pray when a man’s voice sings out the shahada as an alarm.

Some Muslims wake up and retire to bed with the shahada on their lips. Fathers whisper it into the right ear of their newborn babies, and most everyone hopes these are the last words they either utter or hear as they near death.