The greatest thing Allah (SWT) has enjoined is Tawheed (Monotheism).
What is Tawed (Islamic Monotheism)?
Tawheed means declaring Allah (SWT) to be the only God who deserves to be worshipped in truth and confirming all attributes with which He has qualified Himself or that are attributed to Him by His Last Messenger Muhammad (SAW).
What are the aspects of Tawheed?
There are three aspects of Tawheed:
1. Tawheed-ar-Rububiya.
2. Tawheed-al-Uluhiya.
3. Tawheed-al-Asma was-Sifat.
What is Tawheed-ar-Rububiya?
It is declaring Allah (SWT) to be One and Unique
in His work, like creation, sustenance, bringing to life and causing death,
etc.
What is Tawheed-al-Uluhiya?
It is declaring Allah (SWT) as the Only god to whom
all acts of worship must be dedicated such as Salat (prayers), Zakat (poor
tax), Saum (fasting), Du'a (supplications), Intention, etc.
What is Tawheed-al-Asma was-Sifat?
It is an affirmation of all the Divine Names and Attributes of Allah (SWT) in a manner that suits His Majesty, as mentioned in the Quran and the Sunnah.