The word shirk in Arabic means taking a partner, i.e., regarding someone as the partner of another. In terms of sharee’ah or Islamic terminology, shirk means ascribing a partner or rival to Allah in Lordship (ruboobiyyah), worship or in His names and attributes.
So, do not set up equals with Allah while you know (the truth of the matter i.e., that He Alone has the right to be worshipped). [al-Baqarah 2:22]
And they set up partners with Allah so that they may turn (the people) away from His path. Say: ‘Benefit (a few days’) gain; surely you will end up in the Fire.’ [Ibraheem 14:30]
Narrated 'Abdullah (May Allah Be Pleased With Him]:
The Prophet (Peace Be Upon Him ) said one statement and I said another. The Prophet said "Whoever dies while still invoking anything other than Allah as a rival to Allah, will enter Hell (Fire)." And I said, "Whoever dies without invoking anything as a rival to Allah, will enter Paradise." [Volume 6, Book 60, Number 24:Bukhari]
Shirk is the most hated sin by Allah. Allah (swt) says in the Qur'an that Shirk is the greatest sin:
Verily associating partners with Allah is a very grave injustice.’ [31:13]
He (swt) also say:
Surely, Allah does not forgive setting up of partners with Him, and He forgives (any other sin) lesser in degree whom He wills. And whoever sets up partners with Allah certainly fabricates a horrible sin.[4:48]
Assuredly, Allah does not forgive (the sin of) setting up any partner with Him, but He forgives any (sin) lesser than that whom He wills. And the one who associates anything with Allah as His partner has surely strayed far off. [4:116]
Indeed Allah has forbidden Paradise to him who associates partners with Him. And Hell is his abode and the wrongdoers will not find any helpers. [5:72]
