When Hazrat Musa (‘alaihis salaam) requested Allah Ta‘ala to grant him a special and exclusive bounty, Allah Ta‘ala commanded him to recite لا إلاه إلا الله in abundance.

Hazrat Abu Sa‘eed Khudri (radhiyallahu ‘anhu) reports that Nabi (sallallahu ‘alaihi wasallam) said:

عن أبي سعيد الخدري رضي الله عنه : عن رسول الله صلى الله عليه وسلم قال : قال موسى عليه السلام : يا رب علمني شيئا اذكرك به وأدعوك به قال : يا موسى قل لا إله إلا الله قال : يا رب كل عبادك يقول هذا قال : قل لا إله إلا الله قال : لا إله إلا أنت يا رب إنما أريد شيئا تخصني به قال : يا موسى لو كان السماوات السبع وعامرهن غيري والأرضين السبع في كفة ولا إله إلا الله في كفة مالت بهن لا إله إلا الله (حاكم 1/528)

Hazrat Musa (‘alaihis salaam) asked Allah Ta‘ala, “O my Lord! Teach me something by which I may remember you (make your zikr) and call unto you in supplication!” Allah Ta‘ala replied, “O Musa! Reciteلا إلاه إلا الله ”On receiving this answer, Hazrat Musa (‘alaihis salaam) said, “O my Lord! All your servants recite this!” Allah Ta‘ala replied, “Recite لا إلاه إلا الله ”Hazrat Musa (‘alaihis salaam) said to Allah Ta‘ala, “There is no deity besides you, O my Lord! (However) I want something which is exclusive to myself.” Allah Ta‘ala replied, “O Musa! If the seven heavens and their inhabitants and the seven earths were placed into one pan of the scale and لا إلاه إلا الله was placed into the other pan, the pan which contained لا إلاه إلا الله would surely outweigh the other pan.”

The kalimah is the foundation of Islam and has been the first and foremost teaching of all the messengers of Allah Ta‘ala.

Hazrat Abu Hurairah (radhiyallahu ‘anhu) reports that Nabi (sallallahu ‘alaihi wasallam) said:

عن أبي هريرة رضي الله عنه : عن النبي صلى الله عليه وسلم قال : الإيمان بضع وستون شعبة والحياء شعبة من الإيمان (صحيح بخاري #9) و في رواية مسلم من الزيادة : أعلاها لا إله الا الله وادناها إماطة الاذي عن الطريق والحياء شعبة من الإيمان (صحيح مسلم #35) 

“Imaan has more than sixty branches and Hayaa’ is a great branch of Imaan.” In one narration, Nabi (sallallahu ‘alaihi wasallam) said, “The greatest and highest of the branches of Imaan is the kalimah لا إله إلا الله and the lowest of its branches is to remove harm from the pathway, and Hayaa’ is a great branch of Imaan.”

As for the first part of the kalimah, by one believing in the oneness of Allah Ta‘ala one testifies that there is no deity worthy of worship besides Allah Ta‘ala. Similarly, one testifies to Allah Ta‘ala’s oneness in his being and in all his attributes. One accepts that he is the only creator and only being worthy of worship and he is alone in all his attributes (giving life and death, wealth and poverty, success and failure, etc). Everything, in entirety, lies in his hands alone.

لَا اِلٰهَ اِلَّا اللّٰهُ مُحَمَّدٌ رَّسُوْلُ اللّٰهِ 

Translation: There is none worthy of worship besides Allah and Muhammad (Sallallahu ‘Alayhi Wasallam - Peace be upon him) is the messenger of Allah.

The kalimah is the door to entering the fold of Islam. Proclaiming and believing in the kalimah immediately causes one to become a muslim. A person who does not proclaim and believe in the kalimah is not a muslim - even if he has acquired a lot of information regarding Islam. If a person, after living his entire life as a disbeliever, proclaims and believes in the kalimah, he will instantly become a muslim and all his past sins and acts of kufr (disbelief) will be forgiven. Hence belief in the kalimah is the foundation on which Imaan (faith) rests.

The kalimah consists of two parts. The first part of the kalimah contains the teaching of the oneness of Allah Ta‘ala and the second part contains the teaching of the risaalah (prophethood) of Rasulullah (sallallahu ‘alayhi wasallam).