The Arabic word illa is a negative word corresponding to the English except, only and buthttp://dictionary.sakhr.com/idrisidic_2MM.asp?Lang=E-A&Sub=%c5%e1%c7.

Use

It is an often reacurring phrase in the Qur'an

Qur'an

The Quran , also transliterated Qur'an, Koran, Alcoran, Qur’ān, Coran, Kuran, and al-Qur’ān, is the central religious text of Islam, which Muslims consider the verbatim word of God . It is regarded widely as the finest piece of literature in the Arabic language...

, often used to give strength to statements by first negating all possibilities, and then referring to a subject. For example, in the Islamic Creed

Creed

A creed is a statement of belief—usually a statement of faith that describes the beliefs shared by a religious community—and is often recited as part of a religious service. When the statement of faith is longer and polemical, as well as didactic, it is not called a creed but a Confession of faith...

 :

• Arabic
  Arabic language
  Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...
  
   text:
• Romanization:
• English
  English language
  English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
  
   translations:
• I testify that there is none worthy of worship except Allah, and I testify that Muhammad is the messenger of Allah.

This can also be seen in the prayer La hawla wa la quwwata illa billah

La hawla wa la quwwata illa billah

thumb|200|Hawqala-ac4u[[Arabic calligraphy of Hawqala]]The Ḥawqala is an Arabic word referring to the statement la ḥawla wa la quwwata illa billah which is usually translated as "There is no initiative or capability except from God." This expression is mentioned by a Muslim whenever seized by a...

, There is neither change nor power except by means of God.