"Truly, your god is truly One!"
Sahih Bukhari, Volume 9, Book 93, Number 469:
Narrated Ibn Abbas:
When the Prophet sent Muadh to Yemen, he said to him, "You
are going to a nation from the people of the Scripture, so
let the first thing to which you will invite them, be the
Tawheed of Allah. If they learn that, tell
them that Allah has enjoined on them, five prayers to be
offered in one day and one night. And if they pray, tell
them that Allah has enjoined on them Zakat of their
properties and it is to be taken from the rich among them
and given to the poor. And if they agree to that, then take
from them Zakat but avoid the best property of the people."
"[Faith] in One God is the most important and
fundamental principle. It is the bedrock of Islam
and the mainspring of its power. All other beliefs,
commands and laws of Islam stand firm on this foundation.
All of them receive strength from this source.
Take it away, and there is nothing left of Islam."
- Abul A'la Mawdudi, Towards Understanding Islam,
Islamic Foundation, 1980
"The Islamic interpretation of monotheism is more
literal and uncompromising than that of any other
religion. Allah is confessed as being one,
eternal, unbegotten, unequalled, and beyond partnership of
- The New Encyclopaedia Britannica, 15th edition,
"Verily, Allah does not forgive the
ascribing of divinity to anything beside Him, although He
forgives any other sin to whomever He wills: for he who
ascribes divinity to anything beside God has indeed
contrived an awesome sin."